UK ISSN 0032-1400
PLATINUM METALS REVIEW A Quarterly Survey of Research on the Platinum Metals and of Developments in their Application in Industry www.matthey.com and www.platinurn,matthey.com
VOL. 46 OCTOBER 2002 NO. 4 Contents
Catalysis for Low Temperature Fuel Cells 146 Ey M. P Hogarth and I R. Ralph
The Chemistry of the Platinum Group Metals 165 By John Evans
Platinum Metals in Biological and Medicinal Chemistry 166 By Matthew D. Hall An Equilibrium in Catalyst Optimisation and Development? 167 ByG. R. Owen Structural Changes and Their Kinetics in Hydrogen-Containing 169 Palladium Systems By V: M. Avdjukhina, A. A. Katsnelson and G. t? Revkevich
Polymer-Supported Rhodmm Catalysts Soluble in sc-COz 176
9th International Platinum Symposium 177 By R. G. Cawthorn
Recyclable Ruthenium-BINAP Catalysts 180
ACFPower Coatingsm 181 By Paul Williams
Electrically Induced Phosphorescence 187
Abstracts 188
New Patents 192
Indexes to Volume 46 195
Communications should be addressed to: The Editor, Susan V. Ashton, Platinum Metals Review, [email protected] Johnson Matthey Public Limited Company, Hatton Garden, London EC1N 8EE Catalysis for Low Temperature Fuel Cells PART 111: CHALLENGES FOR THE DIRECT METHANOL FUEL CELL
By M. P. Hogarth and T. R. Ralph Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.
The direct methanol fuel cell (DMFC)is a low temperature fitel cell operating ut temperutures of30 to 130°C. The DMFC is powered by CI liquidfie1 (usually considered essentia1,fortransport uses) and is therefore regarded by some as the idea1,fuel cell system. III this piper, the DMFC is cornpared to the hydrogen-fuelled proton exchange mentbrane firel cell (PEMFC) which was discussed in detail in the Jaiiuaty and July issues. While a typical DMFC is less eficient than a PEMFC, work to improve its performance with new electrocatulyst murerials jor utilisation in the membrane electrode assemblies has proved successfiil. This work is described here and some possible commercial uses jor the DMFC are also considered.
Two of the most advanced low temperature developing materials, such as new anode and cath- fuel cells are the proton exchange membrane fuel ode electrocatalysts and new proton conducting cell (PEMFC) and the direct methanol fuel cell polymers, to promote the efficiency of the mem- (DMFC). The DMFC directly consumes liquid fuel brane electrode assemblies (MEiAs) used in the (methanol), while the PEMFC is fuelled by hydro- DMFC stack. Advanced MEA designs have also gen. Operating a fuel cell with liquid fuel is been developed. Since most effort has been direct- considered by some to be essential for transport ed towards increasing the efficiency of the MEA applications - for compatibility with the existing components, the DMFC system itself has petroleum distribution network. The DMFC also remained relatively undeveloped compared to the has some system-related advantages over the PEMFC - particularly for transport use. PEMFC, making it of interest to fuel cell develop- However, interest in producing low tempera- ers. For instance, the DMFC has no need for a fuel ture (< 60°C) ambient-pressure portable DMFC processor (or reformer) to convert a liquid hydro- systems has increased recently. This is because the carbon fuel (gasoline) into a consumable source of power densities now accessible by state-of-the-art hydrogen. This considerably reduces the complex- MEAs may be enough for these systems to ity and cost of the system. The DMFC system does become competitive with leading secondary bat- not require the complex humidification and heat tery technologies. This area could thus become a management hardware modules used in the near-term market oppommity for the DMFC, with PEMFC system: the dute methanol-water mix- transport uses being a longer-term goal, if further tures circulating around the DMFC provide the performance gains can be achieved. necessary humidification and heat management. If it can meet the performance required of a Comparison of PEMFCs and DMFCs commercially viable device, the DMFC system will The PEMFC and DMFC have much in com- be potentially more cost effective than the PEMFC. mon, in particular their MEAs. The MEA and its Performance has been a major problem for the components were described in detail in Part I (1). DMFC: it typically produces only one third of the The MEA of a DMFC usually consists of five lay- PEMFC's power density. Hence, the DMFC com- ers which include gas and liquid diffusion layers, munity has made great efforts to bring the and electrocatalyst layers with a polymeric proton performance closer to that of the PEMFC, and conducting acidic membrane in between (2). The particularly to extend the maximum operating tem- proton conducting membrane acts as an electronic perature. The majority of the work has involved insulator between the electrodes, but allows protons
PhfimmMetals Rev., 2002,46, (4), 146164 146 I Fig. I The perjhnance losses seen in a typical DMFC MEA operuting with dilute MeOH and air at SOT,compared to those in a PEMFC. The PEMFC is operating with pure hydrogen. A list of furtors affecting the eflciencies of both .fuel cells is on the right in the Figure to migrate efficiently from the anode to the cath- tice, the cell voltage in both fuel cells is much less ode. The membrane also functions as a physical than this, see Figure 1. For example, at a current barrier to prevent mixing of the reactants. In ad&- density of 500 mA cm”, the cell voltage is typical- tion, a soluble form of the membrane mated is ly around 0.75 V for the PEMFC (1) and 0.4 V for used to impregnate the electrocatalyst layers to the DMFC (3). Therefore, the power density and extend the membrane interface. This provides a efficiency are considerably hgher in the PEMFC proton conducting pathway. (61 per cent) than in the DMFC (34 per cent). While the structures of the MEAs used in the PEMFC and DMFC are similar, the performance The Effect of Poor Kinetics of each is very different. A comparison of the per- Both types of fuel cell are limited by the poor formance of the two fuel cells and the factors electrochemical activiy of their cutbode-r, for rea- which limit their efficiencies is shown in Figure 1. sons described in Part I (1). This reduces the cell The DMFC has a maximum thermodynamic voltage of both by up to 0.4 V at 500 mA voltage of 1.18 V at 25”C, dehned by its anode and However, unlike the PEMFC (when operated cathode half-cell reactions: with pure hydrogen), the DMFC anode is also h- ited by poor electrochemical activity (kinetic loss [8] Anode reaction: CH30H + H20 = COz + 6H’ + 6e- in Figure 1). This can account for a further loss in E, = 0.046 v (i) cell voltage of more than 0.3 V at 500 mA cm-’ (at Cathode reaction: 3/202 + 6H’ + 6e- = 3H20 900C). E”, = 1.23 V (ii) To increase both the anode and cathode activi- ties in the DMFC, the electrocatalysts employed Cell reaction: CH3OH + HzO + 3/202 = COZ+ 3H20 are unsupported (with high Pt loadmgs of Encd= 1.18 V (ii) usually typically 5 to 10 mg Pt cm-’ for each electrode) In comparison, the PEMFC has a maximum rather than the carbon-supported electrocatalysts thermodynamic voltage of 1.23 V at 25°C. In prac- used in the PEMFC. This Pt loading is too high
Phtinnm MefaLr h.,2002,46, (4) 147 for commercial exploitation of the DMFC (but it methanol concentrations used in the DMFC are does of course dramatically increase the power low, the anode structure has to be designed to allow densities attainable by the MEA). By contrast, typ- both efficient diffusion of the liquid fuel into the ical PEMFC electrodes are carbon-supported electrocatalyst layer and effective removal of the electrocatalysts, loaded at 0.2 to 0.5 mg Pt cm”. product carbon dioxide (COz). Correct design of the anode electrode spucture is very important for Fuel Crossover limiting anode mass iransportlosses ([GI in Figure 1). Another critical effect, which reduces the effi- ciency of the DMFC, is fuel crossover (methanol Anode Electrocatalyst Limitations ~JJOVW[4] in Figure 1). Methanol and water readi- Although the electrooxidation of methanol is ly diffuse through all the commercially available thermodynamically driven (by the negative Gibbs polymeric membrane electrolytes (such as Nafion), free energy change, AG, in the fuel cell), in prac- and significant quantities of methanol and particu- tice, the rate of methanol electrooxidation is larly water pass from the anode to the cathode. severely limited by poor reaction kinetics. To This reduces the cathode efficiency in two ways. increase the efficiency of the anode reaction, it is First, any methanol that comes into contact with necessary to understand the reaction mechanism. the cathode electrocatalyst will reduce the efficien- Indeed, there are now probably over 100 published cy of the oxygen reduction reaction by a compet- papers that deal with identifying the nature and ing electrochemical process - known as the mixed rate limiting steps of this reaction (7). potential effect. Second, the cathode structure The most likely reaction scheme to describe the becomes waterlogged or flooded, and is no longer methanol electrooxidation process is shown in an efficient structure for gas diffusion (mars trans- Figure 2 (Steps i to viii). Only Pt-based electrocat- port loss, [3] in Figure 1). Both these effects can alysts display the necessary reactivity and stability reduce the cell voltage by a further 0.2 to 0.3 V, in the acidic environment of the DMFC. particularly when practical air flows are used. Spectroscopic studies on polycrystalline Pt have In practice, the effects of methanol crossover shown that methanol is electrosorbed in a complex can be reduced to a large extent by careful design process analogous to dehydrogenation. Sequential of the MEA structure or by the application of stripping of protons and electrons is believed to novel membrane materials (4) or cathode electro- take place (Steps i to iv), leading to the formation catalyst materials (5, 6). The use of thick of carbon-containing intermediates, such as linear- membrane materials, such as Nafion 117 (- 180 ly bonded -co,d, and -CHO,d, (8, 9). pn), in preference to those used in the PEMFC, Although the vast majority of these studies have such as Nafion 112 (50 q),is often a sensible been carried out on bulk polycrystalline or single choice. Using a thick membrane does increase the crystal metallic Pt surfaces, it is possible to study cell resistance (ehchu&e ndJtance [5] in Figure 1). the methanol electrosorption process on finely but it is usually easily outweighed by an improved divided electrocatalysts in a single cell. Methanol performance as a result of reduced crossover. electrosorption appears to occur spontaneously A further consequence of the high methanol when the anode and cathode of an MEA are con- crossover rates in commercially available materials nected externally by an electrical circuit. Hence, is that to reduce it, the DMFC anode must be sup- when methanol comes into contact with the elec- plied with dilute methanol fuel, typically 0.5 to 1.0 trocatalyst, an electric current flows between the molar concentration. This presents problems for two electrodes. This occurs for only a brief period system design because, in addition to the methanol of time until the electrocatalyst becomes poisoned fuel, large quantities of water must be stored, with surface-bound intermediates, such as -CO,d,. adding to the size and complexity of the system. It The results of an experiment in which three dif- is particularly awkward for applications where ferent anode electrocatalysts were exposed to a space is limited, such as portable devices. As the dilute methanol/water mixture are shown in
PhfhmMet& Rev., 2002, 46, (4) 148 Fig. 2 A reaction .scheme ilescribing the probable methntiol electrooxidutiorr process (Steps i to viii) )tithin (i DMFC titiode. Only Pt-bciscd electrocatalyst.~ show /he necessary reactivity rind sicrbility in the acidic environment of the DMFC to be ofprclcticnl use
Pt
Figure 3. The electrocatalysts were 40 wt.% methanol (at - 400 s). The charge levelled out Pt/Vulcan XC72R carbon black, 20 wt.% Pt, 10 after a few minutes, suggesting that the electrocat- wt.% Ru/Vulcan XC72R and PtRu black alloy. alyst surface became poisoned and was unable to The loadings on each electrode were: 1 mg Pt cm-* and 0.5 mg Ru cm-2 (ruthenium). Experiments were carried out at 90°C in a 50 cm2 in-house designed single cell using Nafion 112 membrane- based MEAs with Pt black cathodes (4 mg cm-*). The half-cell behaviour of the anode was studied by supplying pure hydrogen to the cathode, which then functioned as a reversible hydrogen electrode @HE) and also as a counter electrode. Electrosorption was carried out under poten- tiostatic control at 75 mV (vs. WE)with a 2 M methanol solution for a period of 20 minutes. This potential was chosen because it is below the threshold potential at which the electrosorbed Fig. 3 Three anode electroccitulysts (locrdings: I mg Pt methanol would be electrooxidised to C02. The em-', 0.5 nig Ru cni') in u single cell. with Nqfiorl 112 membrctne-based MEAs. exposed to dilute methanoUwter cell was then flushed with pure water for a further (it 90°C. The ccithodes are Pt bkrck (4 mg Pt en-'). At 20 minutes to remove any unreacted methanol. - 400 s after methanol contac/, the electroccrtcr1v.st.s produce charge which levels out rrs the su~cicebecomes As Figure 3 shows, a charge was produced by poisoned mid stops reacting. Cyclic voltammetry each electrocatalyst when it came into contact with cmjirmed tin intermediate species was present
PLdnntn Metah b.,2002, 46, (4) 149 I Table I Surface Areas of Electrocatalyst Materials Pt and PtRu Determined with Gas-Phase CO and Electrochemically with CO and Methanol, and the Resulting Stripping Peak Potentials I I Electrocatalyst Electrocatalyst surface area, Stripping peak potential, m2g" Pt or m2 g-' PtRu mv (vs. (RHE) co, co, Methanol, co, Methanol, gas-p hase electrochemical electrochemical electrochemical electrochemical ( E PSAco) (EPSAM~OH)
40 wt.% PtiXC72R 67 40 37 538 438 20 wt.% Pt, 10 Wt.% Ru/XC72R 139 80 78 305 292 PtRu alloy black 83 46 39 302 292
react further with methanol. It was not possible to 2).Water electrosorption is believed to occur lead- quantify the rate of this reaction since a few sec- ing to the formation of -OHdd,species which then onds were required to pass the methanol solution react with the intermediate species to form COz through the flow field and across the entire area of (10,ll).This process results in the saipping peaks. the electrode. The presence of an intermediate As the nature of the surface-bound intermedi- species was confinned by ramping the anode ate was unknown but was believed to be 40-like, potential up to 0.9 V (vs. RHE) at a scan rate of 10 the experiments were repeated but with CO gas mV s-'. This resulted in an electrooxidation peak passing through the fuel cell instead of methanol. (stripping peak) for each electrocatalyst, shown in A CO,d,-stripping peak was recorded for each Figure 4 (corresponding to Steps vi to viii in Figure electrocatalyst, see Figure 4. In addition to the elec-
Fig. 4 Stripping peaks (electrosorbed methanol intermediates and electrosorbed carbon monoxide (CO(,'IJ) .for three mode electrocatalysts. The peaks probably correspond to Steps vi to viii in the reaction scheme of Figure 2
Phrinum Metab b.,2002,46, (4) 150 trochemical measurements, the gas-phase CO Further, the presence of a shoulder on both the chemisorption areas of the electrocatalysts were methanol and CO Stripping peaks also suggests determined. The data are summarised in Table I, that the electrocatalyst contains either two types of and show the CO gas-phase and CO electrochem- reaction site or crystallites with differing activities ical surface areas for each electrocatalyst. The CO that were resolvable by both techniques. gas-phase surface areas correspond to the absolute One final point to consider is the relevance of maximum metal surface area. The electrochemi- the EPSA values determined by each technique. cally determined CO values, however, correspond Although the values in Table I are normalised for to the electrode platinum surface area (EPSACO), the Pt and Ru content of the electrocatalysts, it is which is the total metal area in contact with the not clear how the Ru components interact with proton conducting polymer in the electrode. For CO in the gas-phase and in the electrochemical each electrocatalyst the EPS&O was less than the experiments. For example, the Ru (or Ru oxides) gas-phase value, indicating that not all the electro- may not be covered with a complete monolayer of catalyst in the electrodes was utilised. CO during the electrochemical measurements. Table I also summarises the EPSAMeoHvalues This process is also probably strongly dependent of each anode electrocatalyst, determined using on time, temperature and the partide size of the the methanol electrosorption (or electrosorbate) electrocatalyst. Similarly, the significance of the stripping peak. (7%. dominant surface-bound EPSA values determined with methanol are open inter- mediate was assumed to be Co&) These to debate. Although methanol is believed to pref- were found to agree well with the CO-stripping erentially electrosorb on Pt sites, the process values (EPS&O) for the 40 wt.% Pt/XC72R and probably requires an ensemble of Pt atoms. 20 wt.% Pt, 10 wt.% Ru/XC72R electrocatalysts. Therefore, for complete poisoning, the methanol However, the values for the PtRu alloy black were fragments must be mobile enough to release the Pt somewhat different. A further difference was ensembles so further reaction with methanol can observed in the stripping-peak positions of each occur. electrocatalyst, see Figure 4 and Table I. The Ru- Nevertheless, the use of methanol stripping containing electrocatalysts produced stripping voltammetry appears to give an excellent indica- peaks at much lower potentials than the pure Pt tion of the available electrocatalyst surface area for electrocatalyst, showing that the removal of the methanol electrooxidation. This strongly comple- surface-bound intermediates was promoted by Ru. ments the measurements that are routinely carried This is believed to occur more readily for PtRu out with co. alloys since Ru is more easily electrooxidised than pure Pt, and forms Ru-OHds at lower potentials Better Anode Electrocatalyst Materials (12). The -Had, species are then believed to spill The search undertaken for more active anode over onto neighbouring Pt sites where they react electrocatalyst materials for methanol electrooxi- with -Cods.This occurs at lower potentials than dation in acid electrolyte is illustrated by studies with pure Pt. similar to the one above. The electrocatalyst needs Another interesting observation was made con- to provide both an efficient mechanism for cerning the relative positions of the methanol and methanol dehydrogenation and an efficient mech- -Codd,stripping peaks. For 40 wt.% Pt/XC72R anism to electrooxidise -co,d, to COZ. the methanol stripping peak was observed at a Of great importance are materials that might lower potential (438 mv) than the CO stripping combine with Pt to promote Steps iv to viii in peak (538 mv). This could be an indication that Figure 2, and Ru in particular significantly increas- the pure Pt electrocatalyst was not completely poi- es the activity of Pt for methanol electrooxidation. soned by the methanol, although the similar EPSA Other studies have looked at elements that form values from the methanol (EPSAM,,H) and CO binary alloys with Pt (Ru, Sn, Re, Au, Mo, W, (EPSAco) experiments make this debatable. Pd, Rh (13-20)), and ternary (PtRuSn (21)) and
Phtinwm Metals Rev., 2002,46, (4) 151 -0- Pt tXC72R -X- PtlrlXC72R +-PtPdlXC72R + PtOstXC72R -A- PtRh IXC72R t PtRulXC72R -Xr PtWIXC72R +PtRuRhIXC72R 4 PtGalXC72R -.A.-PtRuSn/XC72R
0 0.1 0.2 0.3 0.4 0.5 06 0.7 0.6 SPECIFIC ACTIVITY, mA cfn-’ Pt
Fig. 5 Half-cell specific uctirity plots,fur Pt cilloy tnaterials in I M sulfuric acidR M methanol at 80°C shoning that Ru-conraining electrocutulysts ure the most cicrive. A lower mode potential corresponds to a more active electrocatalvst for methanol electrooxidution quaternary alloys (PtRuIrOs (22)). each electrode, the half-cell polatisation data were At the Johnson Matthey Technology Centre, corrected to give the intrinsic activity of the elec- the focus of DMFC anode development has been trocatalysts (specific activity, mA cm-’ Pt). Hence, on using carbon-supported high surface area elec- the activity of each anode electrocatalyst could be trocatalysts. Figure 5 presents anode half-cell compared, independent of its surface area. polarisation data for a series of Vulcan XC72R- The half-cell data in Figure 5 show that the supported Pt materials. These include pure Pt, and activities of the materials fall into two distinct alloys of Pt with iridium (Par), palladium (PtPd), bands. The most active electrocatalyst materials - osmium (Ptos), rhodium (PtRh),. tungsten (PtW), those having the lowest potentials - all contain Ru. gaUium (PtGa), ruthenium (PtRu), ruthenium- The elements Rh, 0sand Ga appear to show pro- rhodium (PtRuRh) and ruthenium-tin (PtRuSn). motional effects, but much smaller than that of Ru. Steady-state measurements were performed at Tungsten did not promote methanol electrooxida- 80°C in 1 M sulfuric acid electrolyte containing 2 tion on Pt, and Pd and Ir appeared to inhibit it. M methanol. Prior to the methanol electrooxida- The methanol electrooxidation activity of the tion studies, the in situ electrochemical metal area PtRu was found to be the highest of the binary Pt- (ECA, m2 g-’ Pt) of each electrode was determined based alloys. A number of groups have claimed to using CO stripping voltammetry. Unlike the have developed ternary or even quaternary materi- EPSAco measurement, this value corresponds to als with activities higher than PtRu alloy (23, 24). the maximum available Pt surface area in the elec- The rationale behind some of these materials is trode. The sulfuric acid can make effective contact sometimes unclear and quite often their new mate- with the entire electrocatalyst surface because it rials are compared with what could be considered floods the electrodes, as it also does in the gas- a poor PtRu alloy baseline. Figure 5 also compares phase CO chemisoiption experiment. Thus, the the methanol electrooxidation data of two ternary performance of each electrocatalyst is not limited materials, PtRuRh and PtRuSn. Both Rh and Sn by electrode structure or by the EPSA effects that have been shown to promote the activity of Pt for are seen in the MEAs. Using the ECA value for methanol electrooxidation, but neither were found
PIatinrrm Met& Rm, 2002.46, (4) 152 to co-promote PtRu. This observation led to the used to estimate the bulk alloy composition (from conclusion that only modest improvements in the the Pt lattice parameter) and the average crystallite PtRu activity can be attained by addmg co-pro- size (using Scherrer’s equation (28)). moting elements. Indeed, quite often, adding From Figure 6 (which shows some early work ternary or even quaternary electrocatalyst compo- that used an experimental deposition technique) nents can reduce the production friendliness of the bulk alloy composition and average crystallite the material and dramatically increase its cost. size (as a function of alloy composition) can be Hence, at Johnson Matthey, the electrocatalyst seen. The XRD-determined bulk alloy composi- development work has focused on optimising the tions shown here are a reasonable match to the PtRu alloy. theoretical compositions. Alloys PtwRulo and Pt&uzo had bulk alloy compositions identical to An Optimum P1atinum:Ruthenium Ratio the theoretical compositions, but alloys from There are a number of published papers which Pt7oRu~to Pt&u,O appeared to be Pt-rich. Thus, describe work to determine the optimum PtRu part of the Ru was not being incorporated into the alloy composition for the DMFC anode (25, 26). predominant crystalline face centred cubic (f.c.c.) For this type of study to be carried out successful- PtRu phase but was present either in an amor- ly, the composition of the electrocatalyst must be phous Ru oxide phase or in an amorphous Ru-rich controlled so that the surface structure is repre- PtRu phase - but neither of these phases could be sentative of the bulk alloy composition. (This can detected with XRD. X-ray photoelectron spec- be challenging for carbon-supported electrocata- troscopy (XF’S) measurements suggested that the lysts.) The composition of the electrocatalyst electrocatalyst surface was indeed Ru-rich. surface is determined by the chemical deposition The XRD crystallite size data showed an inter- process used to deposit the particles and/or by any esting effect: the crystallite size of Ptlm was very post-treatment it receives, such as thermal anneal- large (- 12 nm) but fell dramatically as the Ru con- ing. The wide range of methods reported in the tent was increased to 30 at.% and above. The literature for preparing PtRu electrocatalysts there- crystallite size of alloys with theoretical composi- fore probably results in a range of materials with tions between Pt70Ru~and P~~ORU~~was found to different surface compositions. This makes it dif- be between 2 to 3 nm. This suggests that Ru pro- ficult to assess which composition is most active motes the dispersion of the electrocatalyst. The for methanol electrooxidation. There is also evi- effect was most noticeable for materials having dence that different alloy compositions are favoured at high and low temperatures (27). Hence, it is probably only possible to select the most active PtRu alloy phase from a range of com- positions prepared using the same deposition process and post-treatment conditions. In order to determine the most active alloy composition for methanol electrooxidation, a range of PtRu/Vulcan XC72R electrocatalysts was prepared by an aqueous-based slurry route. Each electrocatalyst contained a 6xed Pt loadmg (20 wt.Yo); the Ru loadmg was varied to give a range of atomic compositions from PtlMto PtJtu,,. The Fig. 6 XRD dutu jbr a range af’PtRdYC72R preparation involved codeposition of highly-dis- electrocutu1y.st.s. showing cilloy composition cmd uverage persed mixed oxide particles onto the carbon, ctystallite size. The diagonal dushed line represents the theoreticul cornpodion. These mciteriuls were used to followed by drying and heat treatment. assess the suitahilir?.of a new laboratary-.sccilechemicul Characterisation by X-ray difhction (XRD) was deposition process
Pkadnwm Metah Rey., 2002,46, (4) 153 Fig. 7 Electrochemical dutu recorded in u hulfcell for PtRu ullovs in I M suljirric acid. The effect of the PtRu ulloy compohition is shown on: (i) methunol electrooxidotion uctivit?, at 100 mA mg-' Pt und 80°C in 2 M MeOH; (ii) the ECA (m' g ' PtRu) determined with CO stripping voltummetry ut u sweep rute .f I0 mV s I: (iii) the 1-ulculuted totul electrochemicul nietul ureu (m' g ' PtRu) from the XRD cnwullite size
compositions (Pt&uW to Pt&u7,,) which deviated the least active material, requiring an anode poten- most from the theoretical composition. Therefore, tial of - 0.500 V (vs. RHE). However, its activity the unalloyed amorphous material that may reside increased dramatically as the Ru content was on or near the surface of the PtRu alloy particles increased to Pt70Ru,o,but at higher Ru contents the may help prevent sintering during the deposition activity became constant at - 0.340 V (vs. RHE). or thermal reduction processes. For alloys Pt&ulo Figure 7 also shows the theoretical (calculated and PtsoRuzo this effect was less prominent because from XRD data assuming spherical particles) and all the Ru was incorporated into the bulk alloy. electrochemical (from CO-stripping voltammetry) To investigate the surface electrochemical metal surface areas as a function of alloy composi- behaviour of the PtRu alloy electrocatalysts and tion. The two sets of values compare well; the their activities for methanol electrooxidation, all ECA values of Pt3oRu70 to Pt&uN are the hghest. the electrocatalysts were used to prepare electrodes An examination of the data suggests that two suitable for testing in sulfuric acid electrolyte. effects may control the activity of the electrocata- Aqueous-based Nafion ionomer inks were pre- lysts. First, as the level of Ru was increased in the pared and carbon-fibre paper electrodes were alloy to 30 at.% and above, the ECA of the elec- manufactured using a coating process. trocatalyst increased. The XRD data also suggest Figure 7 shows the half-cell methanol electro- that part of the Ru was not incorporated into the oxidation activity and the ECA (mz g-' PtRu, Pt lattice but may have remained segregated on the determined with CO-stripping voltammetry) for surface of the particles, perhaps as an oxide. each PtRu material. The methanol electrooxidation Further addition of Ru beyond Pt~Rumdid not activities were determined in 1 M sulfuric acid and lead to a relative increase in the amount incorpo- 2 M methanol at 80°C. The electrodes contained rated into the Pt lattice. Instead, the amount of 0.35 mg Pt cm-'. The methanol electrooxidation unalloyed Ru remained essentially the same (as activity is compared at a mass activity of 100 mA shown by the constant deviation of the XRD alloy me-' Pt; electrocatalysts with lower anode poten- composition versus the theoretical composition in tials were the most active. (The mass activity Figure 6). Thus, the methanol electrooxidation corresponds to the current density corrected for activity of all these materials is roughly similar. It the electrode Pt loading.) As expected, pure Pt was appears that good alloying of Ru into the Pt lattice
Plalinwm Met& Rev., 2002,46, (4) 154 I Table II Some Physical and Electrochemical Parameters for Pt Black and Various PtsoRusoAlloy Electrocatalyst I ComDositions I Composition XRD crystallite XRD lattice Calculated surface CO chernisorption metal size, nm parameter, 8, area, rn2 g-' Pt(Ru) area, ECA, m2 g-' Pt(Ru)
20 Wt.% Pt, 10 Wt.% RU 1.9 3.877 174 139 40 Wt.% Pt, 20 Wt.% RU 2.5 3.883 132' 104 PtRu black 2.9 3.882 114 83 Pt black 6.5 3.926 43 24
is required to produce an active electrocatalyst, but Ru electrocatalyst had a slightly larger crystallite that the process of 'tilling the Pt lattice' may also size (2.5 nm), while the PtRu black had the largest enable a stable surface Ru component to be built (2.9 nm). These are excellent dispersions, especia- up - most likely essential for promoting methanol ly for the latter two, and this is very apparent when electrooxidation (1 2). their crystaJlite sizes are compared to that of This contrasts with the proposed mechanism unsupported Pt black (6.5 nm) (HLSPECTM1000). by which PtRu alloy promotes CO tolerance in the The improved dispersions found for PtRu elec- PEMFC at practical anode potentials. The CO tol- trocatalysts compared with a pure Pt electrocat- erance (in PEMFCs) of PtRu is believed to occur alyst at a similar loading on carbon was described because the incorporation of Ru in the Pt lattice in Part I1 (29). The presence of Ru again appears decreases the Pt-COd, bond strength, reducing to promote the dispersion, most probably through the -Codd,coverage (28). Surface Ru only comes small amounts of surface-segregated Ru oxides (or into play at hgher potentials where it promotes surface enrichment with Ru) which prevent sinter- -co&electrooxidation. as in the DMFC. ing. The XRD lattice parameter values for each PtRu electrocatalyst also show a shift from the Anode Electrocatalyst Structure value for pure Pt black. This is not indicative of Unsupported PtRu alloy blacks are the most exactly PtsoRuso alloy but of slightly Pt-rich alloy widely used electrocatalysts employed at the (compared to the theoretical composition). DMFC anode, primarily because they provide very The CO chemisorption metal areas conked high Pt loadings (210 mg Pt cm") to maximise the trend seen in the XRD crystallite size data. The the EPSA in the electrode. Such electrodes are CO gas-phase area of 20 wt.% Pt, 10 wt.% Ru was very active for methanol electrooxidation but are the highest (139 mz g-' PtRu); slightly lower (104 too expensive for most commercial applications. mzg-' PtRu) for 40 wt.% Pt, 20 wt.% Ru; and low- To investigate whether the metal hdng could est (83 mz g-' PtRu) for PtRu black alloy, although be reduced to a more economical level and find this last value is much higher than that of the Pt the effects on performance, a series of PtRu alloy black (24 m2 g-' Pt). The difference between the electrocatalysts of composition Pt&uw was pre- calculated and CO gas-phase areas is probably due pared. The materials were PtRu black (HiSPEC" to obscuring of the metal crystallites, and was very 6000), and two Vulcan XC72R-supported electro- evident for the Pt black sample. catalysts of composition 20 wt.% Pt, 10 wt.% Ru (HtSPECm 5000) and 40 wt.% Pt, 20 wt.% Ru. Specific Activity for Methanol Elcctrooxidation The crystallite sizes and lattice parameters were To find the methanol electrooxidation activity determined by XRD, see Table 11. The smallest of the electrocatalysts, flooded steady-state half- crystallite size was 1.9 nm for the 20 wt.% Pt, 10 cell experiments were performed in 1 M sulfuric wt.% Ru electrocatalyst. The 40 wt.??Pt, 20 wt.% acid and 2 M methanol at 80°C. Electrodes were
Phfinnm Metals h.,2002,46, (4) 155 Fig. 8 Flooded anode half-cell polarisation dafuut 80°C in I M sulfuric acidn M methuno1,for three PtRu materials with a Pt loading of - I mg Pt cm '. The intrinsic activity of each material was cornparable under these conditions
prepared using electrocatalyst-containing aqueous The electrodes described above (with 1 mg Pt cn-3 Nafion inks, with a loacllng of - 1 mg Pt cm-'. were used to prepare MEAs using Nafion 112 Figure 8 shows the specific activities of the three membrane and Pt black cathodes (4 mg Pt cm-2). PtRu electrocatalyst materials; under the reaction Figure 9 shows the results of pseudo anode conditions, the methanol electrooxidation activi- half-cell (or half MEA) experiments at 90°C. In ties were comparable. That is, the intrinsic kinetic these experiments, the anode of the MEA was sup- activity of the electrocatalysts was unaffected by plied with 2 M methanol fuel and the counter the electrocatalyst structure and no significant elec- electrode with pure hydrogen. The fuel cell was trode structure effects were observed. The lack of then driven by a potentiostat and the anode poten- electrocatalyst structure effects is probably due to tial (vs. RHE) was measured as a function of the the sulfuric acid electrolyte penetranng the entire current density. The resistance of the MEA was electrode structure, and utilising all the electro- determined using current-interrupt techniques. catalyst. Although the intrinsic activities of the electro- catalysts had been identical in sulfuric acid MEA Anode Performancc electrolyte (Figure 8) this was not the case when To study the effect of the anode electrode these electrocatalysts were employed in the anode structure on the MEA performance, a series of of an MEA. Within the MEA, their anode perfor- experiments was carried in a 3 cmz micro-fuel cd. mance appears to be linked to a number of factors
Fig. 9 Pseudo anode halfcell (or half MEA) experiments at 90°C. The anode potential (w. RHE) is measured as afunction qj'current densip,for the three PtRu muterials. 2 M Methanol was supplied to the anode and pure hydrogen to the cathode. The 40 wt.% Pt, 20 wt. % Ru electrocatalyst had the highesr performance, shown b?j its lower potential
Ph%immMe& Rev., 2002,46, (4) 156 Fig. 10 Single cell polurisation curves showing the effect of the anode structure on the MEA performance. The highest anode perforniance is given by 40 wt.% Pt, 20 wt.% Ru. The anode loading is I mg Pt ctd. The operating temperature is 90°C,and Najion I I7 membrane is used. The fuel is 0.75 M MeOH (Ahf
Piatinurn Metah REV.,2002,46, (4) 157 pressure and at a flow 4.5 times in excess of ionic resistance and thus increased MEA perfor- stoichiometry = 4.5) (a stoichiometry of 1 is mance. They also help to reduce the MEA cost. the amount needed to sustain the current). The For the DMFC, it would be advantageous to use cathode was supplied with unhumidified air at a thinner membrane materials to reduce the ionic pressure of 30 psig at a flow 5 times stoichiometry resistance of the MEA. However, there is a sensi- (L= 5). ble lower thickness limit beyond which the rate of The data in Figure 10 show the same clear trend methanol crossover becomes too hgh and/or the as the pseudo anode half-cell data in Figure 9. The membrane is no longer strong enough to maintain MEA containing the 40 wt.%, Pt, 20 wt.% Ru elec- the large pressure differentials often needed. trocatalyst gave the highest performance (0.5 V at 228 mA cm-’) compared with 20 wt.% Pt, 10 wt.% Cathode Improvements Ru (0.5 V at 170 mA ern-') and PtRu black (0.5 V With careful design of the cathode, it has been at 187 mA cm-’); all had the same Pt loading of 1 possible to use Nafion 112 membrane as an alter- mg Pt cm-’. Figure 10 also gives current-interrupt native to Nafion 117, without significant loss in resistance data for the same series of MEAs, also performance. Data from a 50 cmz single cell con- showing that the structure of the anode did not taining MEAs with Nafion 117 and Nafion 112 influence the resistance of the MEA. That is, the membranes is shown in Figure 11. Both MEAs performance difference was entirely due to the contained a 40 wt% Pt, 20 wt% Ru (1 mg Pt ad) change in anode structure. anode and a Pt black (4 mg Pt cm-’) cathode. Cell Therefore it appears that 40 wt.% Pt, 20 wt.% voltage data were recorded at 90°C with 0.75 M Ru gives an MEA performance superior to those methanol (1~4~= 4.5) and pressurised air (30 of 20 wt.% Pt, 10 wt.% Ru and PtRu black. psig, h, = 5). In a second (pseudo half-cell diag- Excellent single cell performance have been nostic) experiment, the anode potential was attained with MEAs containing only 1 mg Pt cm-’ determined by passing pure hydrogen across the with power densities exceeding 100 mW cm-’. This cathode (instead of air) and the fuel cell was driven shows that careful choice of the anode structure is by an electric load. Hence, the anode and cathode important to maximise DMFC MEA performance potentials could be decoupled from the cell volt- and that the levels of PtRu electrocatalyst can be age. Current-interrupt measurements were used to reduced significantly fiom the 2-10 mg Pt cm” determine the MEA resistance. levels that are traditionally employed. Under these conditions, the MEA with Nafion 112 had the better performance than with Nafion The Effect of Membrane Thickness 117, especially at lugher current densities. This was Nafion 117 membrane is the preferred electrolyte shown to be mainly a resistance effect - the resis- for the DMFC. It is the thickest (- 180 p)available tance-corrected data for both MEAs were commercial fuel cell membrane. The rate of methanol comparable (except that the cell voltage of the crossover through Nafion 117 is low compared to, Nafion 112 MEA was about 10 mV lower at low for instance, the thinner Nafion 112 membrane (50 current densities, probably due to enhanced p).New membrane materials to help reduce the methanol crossover). This observation was con- methanol crossover rate are being developed, but firmed by the anode and cathode half-cell data for it is unlikely that any of the current candidates will the MEAS.As expected, the anode half-cell poten- completely eliminate it as all low-temperature proton tials of both MEAs were very similar. In the conducting polymer materials only function efficiendy Nafion 112 MEA the cathode potential was only in a fully hydrated state. Methanol, being completely about 10 to 20 mV lower than in the Nafion 117 miscible with water, is carried by the water as it MEA due to the enhanced crossover rate through diffuses through the membranes. the thinner membrane. In the PEMFC, thinner membrane materials Figure 11 also shows the cathode potential for (such as 30 p)are preferred as they offer reduced the same Nafion 112 MEA when it was operating
Phfinum Met& Rcv., 2002,46, (4) 158 Fig. II A comparison of Najion 117 and Najion 112 membranes in MEAT.Both MEAs hove (I 40 wt.% Pt, 20 wr.% Ru anode (I mg PI cni ') and a Pt black cathode (4 mg Pt cm-'). The data were recorded in a 50 cm2 single cell at the operating temperature of 90°C with 0.75 M methanol,fuel (LOU= 4.5) and pressurised air (30 pig. A,,, = 5). hi a pseudo halj-cell experiment, pure hydrogen was pussed across the cathode to help determine the mode potential. The Nujiori 112-bused MEA had the higher performance (especially at higher current densities) due to reduced membrane resistance as a PEMFC. Instead of methanol and dry air, it pressurise them). The cathode exhaust gas from was supplied with humidified hydrogen and the fuel cell stack must also be cooled efficiently to humidified air, respectively, (both at 30 psig). The remove any methanol (from crossover) and water cathode potential in PEMFC-mode is only slightly vapour. This places a high energy demand on the higher (10 mv) than in DMFC-mode (but is slight- fuel cell system. A lower air flow, preferably equiv- ly lower than the cathode potential for the Nafion dent to a stoichiometry of 2 (A- = 2) or less, is 117 MEA in DMFC-mode).This suggests that the thus desirable. Pt black-based cathode structure used in these Figure 12 shows the performance of a Nafion MEAS has good methanol tolerance and indicates 117-based MEA, of similar construction to that in that the cathode structure can be optimised to Figure 11. Single cell measurements were carried make it essentially methanol tolerant. However, out at 30°C with 0.75 M methanol fuel (~M,OH = these experiments were carried out with relatively 4.5) and pressurised air (30 PSI&, but at the lower high air flows (hk = 5) and at high pressures which air flow rate, h, = 2. Under these conditions, the reduce the effects of crossover to some extent. MEA performance was very similar to that of the MEA in Figure 11 which was operatingwith a hgh Reducing the Cathode Air Flow air flow (L= 5). The air flow rate in the single cell shown in Pseudo half-cell experiments were carried out Figure 11 is too high for most practical fuel cell to decouple the anode and cathode half-cell poten- applications (large volumes of air require energy to tials in the MEA. The cathode potential was found
Phtimm Mefdb., 2002,46, (4) 159 Fig. 12 Data recorded at low airflows to the cathode. = 2, in n 50 cm' single cell with a Nafion I1 7 MEA. The anode is 40 wt.% Pt, 20 wt.% Ru (1 mg Pt cm-') and the cathode is platinuni bkrck (4 mg PI cnii'). The operating temperuture is 90°C und the,fuel supplied to the anode is 0.75 M methanol (LOH= 4.5); the nir is pressurised (30 psig). The cell perjhnance under the low airflow conditions is compunible to that at higher air,flows. This demon.strutes the good methanoWwuter tolerance of the cathode
to be only 510 mV lower under the low air flow (Pt black, 4 mg Pt cm-2). To reduce this loading, conditions, showing the excellent water and work was undertaken to develop carbon-support- methanol tolerance of the cathode. The cathode ed Pt electrocatalysts of much hgher surface area potentials were also compared in DMFC- and than Pt black electrocatalyst (24 mz g-' Pt) (1). A PEMFC-modes, and were found to be identical reduction in Pt loading from 4 to 1 mg Pt cm-2was under the low air flow condition. Thus, the effects investigated, and providmg that the methanol tol- of methanol crossover can be significantly reduced erance is comparable to that of Pt black, no impact by careful design of the cathode and the perfor- on performance was expected. The new materials mance can be maintained at low air flows. Indeed, must also be able to cope with the high levels of methanol-tolerant materials (6) may not be water and methanol found at the DMFC cathode. required under these conditions, especially with In Figure 13, data from a 25 cm2 single cell Nafion 117 membrane. measured at 90°C for three MEAs is shown, one is based on Pt black (4 mg Pt cm-') and two are Reducing Cathode Electrocatalyst Loading based on carbon-supported Pt cathodes (1 mg Pt The DMFC anode electrocatalystdevelopments cm-'). Methanol (0.5 M) was supplied to the anode described so far have been aimed at reducing the = 3) and pressurised air to the cathode (30 Pt loading to 1 mg Pt ern-', while maintaining per- psig, h, = 10). Cathode A was based on 40 wt.% formance. This has been achieved with 40 m.%Pt, Pt on carbon @CA 60 m2 g-' Pt) of similar con- 20 wt. YORu/Vulcan XC72R. By comparison, in struction to that used in the PEMFC. Cathode B the PEMFC the typical Pt electrocatalysts used in was based on a 60 wt.% Pt on carbon (ECA 45 m2 the cathodes are also supported on Vulcan XC72R, g-' Pt) and was optimised for DMFC operation. but the loading is only 0.2 to 0.7 mg Pt cm-2 which The performance of the MEA with cathode A was gives an excellent MEA performance (1). slightly lower than the Pt black cathode. The MEA AU the DMFC single cell data described here with cathode B performed comparably to the Pt have used MEAs containing high loaded cathodes black cathode, showing that the cathode Pt loadmg
Platinnm Metalr Rev., 2002,46, (4) 160 Fig. 13 Cell voltage data recorded in u 25 cm' single cell of the performances of three MEA cathodes at u 90°C operating temperature. The Pt black cathode is loaded at 4 mg Pt cm-'. Cathode A (40 wt.% Pt/ carbon) and Cuthode B (60 wt.% Pt/carbon) are loaded at I mg Pt cm '. Methanol fuel (0.5M) was supplied to the anode (b,.,~= 3). und pressurised uir (30 pig) to the cathode at high flows (A",,= 10). The anode was 40 wt. % PI, 20 wt.% RulXC72R (1 rng ft cm ') can be reduced significantly without performance been done to increase the MEA performance at loss. Further optimisation is expected to bring the lower temperatures and pressure (20 to 60"C, Pt loading to the levels used in the PEMFC. ambient air pressure). Often, the MEAs used in portable ambient DMFC systems have been opti- Portable DMFC Applications mised for higher operating temperatures and Recently, the tremendous advances attained in pressures, which may not be the best option to power densities by the DMFC have prompted maximise power density. Tailoring the MEA com- companies, such as Smart Fuel Cell (Germany); ponents, including the electrocatalysts, substrate Manhattan Scientific, MTI and Motorola (U.S.A.); and membrane, may improve the performance and Toshiba gapan) to establish ambient micro- further and is a hgh priority for device developers, DMFC programmes to target the 1-100 W power as improvements in the stack power/size ratio will range. While the power densities offered by the allow more straightforward miniaturisation. DMFC are considerably less than those from the PEMFC, the DMFC can still generate sufficiently Miniaturising the Fuel Cell Stack high energy densities to make it an attractive alter- Figure 14 presents 50 cmz single cell data for an native to secondary batteries for a wide range of MEA based on Nafion 117 membrane, a 40 WL% applications. Miniaturisation of the DMFC system Pt, 20 wt.% Ru/XC72R anode (1 mg Pt cm-') and is also simpler. With liquid fuel, the main a Pt black cathode (4 mg Pt cd). The data were advantage is the convenience of almost instant measured at 40,60 and 80°C with 0.5 M methanol recharging, by replacing a spent fuel cartridge - an (flow rate 6 ml mid) and ambient air (< 0.3 psig advantage over rechargeable batteries. The DMFC inlet pressure) at low flows (L= 2). Although this is therefore being targeted at applications such as MEA was optimised for hqgher temperatures and mobile phones, notebook computers and video pressures, its performance under low pressure cameras where rapid recharging is advantageous. conditions was good. The data is summarised in To date, the most efficient DMFC systems are Table In together with projected fuel cell stack almost all exclusively designed to operate at hgh- volumes (cm') for a range of devices. er temperatures and pressures where the power The fuel cell stack volumes were calculated densities are the hghest. Most MEA development based on a 3 mm cell pitch (the thickness of one has focused on increasing the performance in the bipolar flow field plate and one MEA), 10 mm temperature range 80 to 130°C and little work has thick stack end plates and an MEA membrane
Platinum Metah Rev., 2002, 46, (4) 161 Fig. 14 Single cell data for an MEA based on Nufion 117 with an anode of 40 wt.% Pt, 20 wt.% RdXC72R (I mg Pt cm") and a Pt black cathode (4 mg PtTem -2 The temperatures were 40,60 and 80°C with 0.5 M methanol fuel supplied to the anode (flow rate 6 ml mini') and ambient air (< 0.3 pig inlet pressure) at flows (a,,,= 2) to the cathode. At 40°C the cell voltage was 0.409 V and power density 21 mW cm-2;at 60°C the cell voltage was 0.419 V and power density 42 m W crn-'; and at 80°C the cell voltage was 0.440 V and power density 66 m W cm border of dimensions 5 mm x 5 mm x 5 mm x 10 tion of the overall volume of the stack. When mm for edge sealing (the 10 mm dimension operating at 4O"C, the projected stack volume includes provision for porting - the holes cut into based on current MEA technology is 823 cm3 the membrane to allow the gases and liquids to (requiring 24 MEAs of active area 61 cm'). If the flow). The calculation does not include the volume temperature of the fuel cell stack is increased to 60 of the fuel pump, the air blower or the fuel tank. and 80"C, the volume of the stack decreases to 430 The projected stack volumes are based on the and 334 cm3, respectively. Temperature thus has a power density of the MEA increasing by a factor large effect on stack volume. When the tempera- of two. ture is increased from 40 to 60°C the stack volume The htst example in Table I11 shows, that to almost halves. The stack volumes are very attrac- generate 1 W of power at a stack voltage of 3.6 V tive; when operating at 60"C, the approximate (typical cell phone requirements) when operating dimensions of a 30 W 10 V stack would be 5.5 cm at N"C, 9 MEAs of active area 5.4 cm2 are x 5.5 cm x 14 cm. When operating at 40"C, with a required, giving a projected stack volume - 63 cm3 doubled MEA power density, the projected stack - far too large to fit a modern cell phone. volume is again significantly reduced from 823 to Doubhg the power density produced by the MEA 441 cm3. At 60 and 80"C, the impact on the stack would only modestly reduce the stack volume to - volume is less marked, decreasing from 430 to 261 42 cm3because the end plates and MEA edge seals cm3 and from 334 to 191 cm3, respectively. Again, are responsible for a large proportion of the stack these are very attractive stack volumes and show volume. This demonstrates that miniaturisation of why the DMFC is being rigorously developed as a the DMFC to fit a cell phone will be challenging. secondary battery replacement device. The other examples shown in Table III corre- spond to larger 30 W 10 V devices operating at 40, Extending Upper Temperature Limit 60 and 80°C. The larger devices utilise volume While the power densities produced by low more effectively, primarily because the end plates temperature ambient pressure DMFC stacks have and edge seals represent a much smaller propor- become attractive enough to drive its near term
PUnum Metals h.,2002,46, (4) 162 Table Ill Ambient Pressure DMFC MEA Performances and Fuel Cell Stack Dimensions*
Stack Stack Stack Current Number MEA Cell Power Stack power, voltage, temp., density, of MEAs activeactive area,area, voltage, density, volume,
W V OC mA cm-' in stack cmzcmz V mWcm2 cm3
1 3.6 40 50 9 5.45.4 0.409 20.5 63 (2.8)(2.8)** ** (0.409) (40) (42) 30 10 40 50 24 61 0.409 20.5 823 (31(31 ) ) (0.409) (40) (4411 30 10 60 100 24 3030 0.41 9 42 430 (1(16) 6) (0.419) (80) (261) 30 10 80 150 23 20 0.440 66 334 (11)(11) (0.440) (120) (191)
* Data rim u 50 cm' single cell for an MEA based on Na&m 117 memhmne with on anode of 40 wt.% PI, 20 wt.% Ru/XC72R (1 mg Pt cn-f j and a PI block ruthode (4 mg Pt em-')). Methanol fuel 0.5 M (flow rate 6 ml mid)is supplied to the anode and ambient air (< 0.3 psig inlet pressure) orflow (&,,, = 2) is supplied to the cuthode. "This value and 011 other volues in brackets are projections based on increasing the power density of the MEAs by a,fucror of two
commercialisation, some argue that longer term amounts of low grade heat must also be removed transport applications should be targeted. The from the stack and radiated to the surroundmgs. DMFC system, and the reformer-PEMFC system, However, the size resmctions, for example, of an are considered to be good options for transport automobile make this difficult to achieve effec- uses, but the DMFC efficiency is poor compared tively, and has led some to believe that the fuel cell to the PEMFC. On the other hand, the PEMFC stack operating temperature must be increased stack must be humidified so the hydrogen (refor- beyond 100°C. Heat management would then be mate) and air are saturated with water vapour. less critical. Without humidification the MEA will dry out and This presents an ideal opportunity for the eventually fail due to resistive heating and pin-hol- DMFC, with its dilute methanol fuel solution pro- ing of the membrane. In addition, the large vidmg it with the necessary humidification. The
Fig. 15 The effects of operating temperatures 90 und 130°C on u DMFC single cell with a Narfion II 7-based MEA. The anode is 40 nit. % Pt. 20 wt. % Ru (I mg Pt cmn ')); the cathode is Pt black (4 mg Pt ern-'). Pressui-ised air (30 pig)jlows (L= 2) to the cathode and 0.75 M methanol = 4.5) is supplied to the anode. At 90°C the MEA perfortnunre is - 330 mA c111i~at 0.5 V A! 130°C the MEA performance is - 530 mA mi2at 0.5 V (or 500 mA cn-' ut 0.510 V) I
PIatinum Metals b.,2002,46, (4) 163 large volumes of water circulated around the stack 8 T. Iwasita and F. C. Nan, J. Ekctmanal. Cbem., 1991, help to keep the membrane humidified at temper- 317, (1-2), 291 9 P. A. Christensen, A. Hamnett, J. Munk and G. L. atures where the PEMFC membrane could not Troughton, J. Ekdmanal. Cdmr., 1994,370, (1-2), 251 operate. 10 S. Wasmus and A. Kuver,J Ekctmad Cbem., 1999, Figure 15 presents DMFC single cell data for a 461, (1-2), 14 Nafion 117-based MEA employing 40 wt.% Pt, 20 11 A. Wieckowski,J. Ekdmnal. Cbem.,1977,78, (2), 229 12 A. Aramata, M. Masuda and K. Kodera, J. wt.% Ru anode (1 mg Pt cm-’) and a Pt black catt- Ekctmcbem. Soc., 1989, 136, (ll), 3288 ode (4 mg Pt cm-’). The design of the MEA is 13 P. Waszczuk, G.-Q. Lu, A. Wieckowski, C. Lu, more advanced than previously presented. It is C. Rice and R. I. Masel, Ekctmcbim. Ada, 2002, 47, (22-23), 3637 supplied with 0.75 M methanol @,McOH = 4.5) and 14 B. Beden, F. Kadirgan, C. Lamy and J. M. Leger, pressurised air at low flows &,, = 2). At 9O”C, the J. Ekdmnd Chem., 1981,127, (1-3), 75 hEA performance is - 330 mA cm-2 at a cell volt- 15 M. Watanabe and S. Motoo, J. Ekctmanal. Cbem., age of 0.5 V, which is significantly higher than 1975, 60, (3), 259 presented earlier. Due to the advanced design of 16 M. Watanabe, Y. Furuuchi and S. Motoo, J. Ekctmand Cbem., 1985,191, (2), 367 the MEA, its performance increases dramatically at 17 M. Gotz and H. Wendt, Ekhcbim. Acta, 1998, 43, hgher temperature. Hence, at 130°C the perfor- (24), 3637 mance was about 530 mA m-’ at 0.5 V (or 500 18 M. P. Hogarth, P. A. Christensen and A. Hamnett, ‘Electrooxidation of methanol on carbon supported mA cm-’ at 0.510 V). The current-interrupt resis- finely dispersed Pt-Ru catalyst’, Proc. First Int. Symp. tance was found to be unchanged at 130°C on New Materials for Fuel Cell Systems, Montreal, showing that the MEA was well humidified. Quebec, Canada, 9-13 July, 1995, pp. 310-325 level of performance brings the DMFC 19 Y.-C. Liu, X.-P. Qiu,Y.-Q. Huang and W.-T. Zhu, J. This PotverSonms, 2002,111, (l), 160 much closer to that of the PEMFC and strongly 20 G. L. Troughton and A. Hamnett, BuL Ekctmcbem., suggests that with further modest improvement in 1991, 7, (ll), 488 power density, the DMFC system could success- 21 W. T. Nappom, H. Laborde, J.-M. Gger and C. Lamy, J. Ekctmanal. Cbem., 1996,404, (l), 153 fully compete with the reformer/PEMFC system. 22 B. Gurau, R Viswanathan, R Liu, T. J. Lafrenz, K. L. Ley, E. S. Smotkin, E. Reddington, A. Acknowledgements Sapienza, B. C. Chan, T. E. Mallouk and S. The financial assistance of the EU is acknowledged, under Sarangapani, J. Pbs. Cbem. B, 1998,102, (49), 9997 the framework of the Non-Nuclear Energy Programme Joule III 23 2.Jusys, T.J. Schmidt,L. Dubau, K. Lasch, J. Garche Contract,JOE3-ClY5-0025. The contributions of past and pre- and R J. Behm, J. PotverSoum, 2002,105, (2), 297 sent members of the Johnson Matthey fuel cell research group 24 W. C. Choi, J. D. Kim and S. I. Woo, Catal. T+, are acknowledged: S. Ball, N. Collis, S. Cooper, J. Denton, D. 2002,74, (W),235 Fongalland, M. Gascoyne, K Goodman, H. G. C. Hamilton, G. 25 W. H. Lizcano-Valbuena, V. A. Paganin and E. R A. Hards, K L. Hogarth, G. Hoogers,J. Keatmg, D. Lonergan, Gonzalez, Ekctmbim. Acta, 2002,47, (22-23), 3715 D. Peat, E. Smith, B. Theobald, D. Thompsett and N. Walsby. 26 H. N. Dinh, X Ren, F. H. Garzon, P. Zelenay and S. Gottesfeld, J. Ekctmand Cbem., 2000,491, (1-2), 222 References 27 H. A. Gasteiger, N. Markovic, P. N. Ross and E. J. Cairns, J. Ekctmchem. Soc., 1994,141, 1795 1 T. R Ralph and M. P. Hogarth, Phtinum Metah REV., 0, 2002,46, (l), 3 28 P. W. Atkins, “Physical Chemistry“, 4th Edn., Oxford University Press, 1990, p. 622 2 G. Hoogers, “Fuel Cell Technology Handbook”, 29 R Ralph and M. P. Hogarth, Pkdnnm Metah Rm, CRC Press LLC, Boca Raton, 2002, Chapter 7 2002, 46, (3), 117 3 M. P. Hogarth and G. A Hards, Pkdinum Metah REV., 1996, 40, (4), 150 4 J. Kerres, W. Zhang, L. Jorissen and V. Gogel, J. The Authors New M&. Ekctmchem. Syst., 2002, 5, (2), 97 Martin Hogarth is a Senior Scientist at the Johnson Matthey Technology Centre and has worked in the area of DMFCs since 5 N. Alonso-Vante and H. Tributsch, Nature, 1986, 1992. His main interests are the development of new 323,431 electrocatalyst materials and high-performance MEAs for DMFCs. 6 R. W. Reeve, P. A. Christensen, A. Hamnett, S. A. He is also interested in novel high-temperature and methanol- Haydock and S. C. Roy, J. Ekctmcbem. Soc., 1998,145, impermeable membranes for the PEMFC and DMFC, respectively. (lo), 3463 Tom Ralph is the Head of Electrochemical Engineering at the 7 R Parsons and T. VanderNoot, J. Ekctmand Cbem., Johnson Matthey MEA manufacturing facility based at Swindon. His 1988, 257, (1-Z), 9 main interests are the development of MEAs for PEMFC and DMFCs.
Platinwm Metah Ray., 2002,46, (4) 164 The Chemistry of the Platinum Group Metals A REPORT OF THE EIGHTH INTERNATIONAL CONFERENCE
By John Evans Department of Chemistry, university of Southampton, Southampton SO17 1BJ, U.K.
The themes of the Eighth International Edinburgh, U.K) described how his work on Conference of the Chemistry of the Platinum coordination spheres interacted with DNA bases is Group Metals (PGM8), held at the University of being extended to organometallic centres. Southampton, from 7th to 12th July 2002, covered Control and exploitation of coordination a broad spectrum from the chemistry of these fas- spheres was preeminent in the programme. Many cinating elements, ranging through examples were elegant, such as the helicate com- Organometallic chemistry plexes of open chain tetra- and hexa-dentate Coordination and supramolecular chemistry phosphines (Bruce Wild, Australian National Biological and medicinal chemistry University, Canberra) and osmabenzenes and Surfaces, materials and crystal engineering fused osma-aromatics (Warren Roper, University Photochemistry and electrochemistry of Auckland, New Zealand), while others chal- 9 Catalysis and organic syntheses, to lenged conventional thinking, such as the careful Theoretical chemistry and physical methods. design of complexes with monodentate phos- The attendees also found time to cruise down phines acting as bridgmg ligands (Helmut Werner, Southampton Water (in mist and rain), visit University of Wiirzburg, Germany). Probably the Stonehenge and Salisbury (only a little rain), walk ‘simplest’ hgand sets were presented by Gary through in the New Forest (totally dry!), and dine Schrobdgen (McMaster University, Canada) who under Kmg Arthur’s Round Table in the Great compared the htgh oxidation states of osmium and Hall in Winchester. xenon (these elements have the widest +8 oxida- But the open and challenging atmosphere was tion state chemistry). The simplicity of the the most apparent hallmark of PGM8. Scientists formulae belied the technical challenges of unrav- with a breadth of approaches shared their differing elling this chemical frontier. experience and targets around common chemical For the most part, ligand sets were chosen to foci, and these can be exemplified by an overview engender attractive physicochemical properties. of the reports of the invited speakers. These included the luminescent properties of ter- The wel-established antitumour activity of cis- pyridyl complexes of iridium and ruthenium platin and carboplatin, and the onset of tumour (Gareth Williams, University of Durham, U.K), resistance to them, was discussed by Lloyd Kelland and the non-linear optical materials based upon (St. George’s Hospital Medical School, London, dendrimeric oligomers of rutheniumQI) bipyridyls U.K.); and here there siill remain many important (Hubert Le Bozec, Universitt de Rennes 1, targets. Phase I trials of a ruthenium(I1I) complex France). Dendrimers and other polymeric architec- were reported by Gianni Sava (University of tures (rings, chains and helices) have been Trieste, Italy), and these show promise for a selec- synthesised with impressive control by Shgetoshi tive effect on lung metastases. Indeed, ruthenium Takahashi (Osaka University, Japan), and Ian complexes occupied a significantlyimportant posi- Manners (University of Toronto, Canada) tion in the biological and medicinal chemistry described his control over the synthesis of differ- theme, with Jackie Barton (Caltech, U.S.A.) using ent types of ferrocenyl polymers. them to monitor electron transfer ranges and iden- Catalysis was one of the recurring reasons for tify the effect of oxidative damage on the ligand design, with Duncan b Bruce (Univertsity of conductivity of DNA. Peter Sader (University of Exeter, U.K) demonstrating that metallorganic
Phtinnm Metalr Rm, 2002,46, (4), 165-168 165 Platinum Metals in Biological and Medicinal Chemistry By Matthew D. Hall, Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW 2006, Australia
The Eighth International Conference on the thrust of platinum metals in medicinal chemistry, Chemistry of the Platinum Group Metals provided the emergence of several promising ruthenium an ideal opportunity for researchers to report their complexes with antimetastatic and antitumour latest results on research and development in the activity was described by Professors G. Sava field of biological and medicinal chemistry with (University of Trieste, Italy) and P. J. Sadler respect to the platinum metals. A number of excit- (University of Edinburgh, U.K.), respectively. ing new directions have emerged in this field, and Complexes trialled by Sava have been shown to these are summarised below. localise in the lung basement membranes, not in Professor J. K. Barton (Caltech, U.S.A.) opened DNA like many platinum drugs, thus preventing the proceedings, describing the elegant use of met- lung cancer metastasis. Sadler described the devel- allointercalators to probe charge migration through opment of RuQI) arene complexes with reduced DNA. DNA base mismatches and drug lesions toxicity, non-cross-resistance and a different (including those from cisplatin) on DNA can be spectrum of activity to platinum compounds. characterised using this method. Her research Structure-activity relationships have been devel- group is currently embarlung on exciting in yitro cell oped and highly selective DNA binding has been studies using these novel probes. demonstrated. While it is clear that the develop- The current status of several platinum drugs in ment of further platinum chemotherapeutics is an clinical studies was reviewed by L. R. Kelland (St. ongoing endeavour, the emergence of active ruthe- George’s Hospital Medical School, London, U.K.) nium compounds with the potential to enter clinical who described the challenge of drug resistance that trials demonstrates that the medicinal chemistry of needs to be faced in future drug development. the platinum metals now has even wider potential. While cisplatin and oxaliplatin remain successful in The Author the clinic, novel such as and drugs JM216 BBR3464 Matt Hall is a Ph.D. student at the Centre for Heavy Metals are currently under evaluation. Professor T. G. Research, University of Sydney, working on the biological fate of Appleton (University of Queensland, Australia) Pt(lV) antitumour complexes under the supervision of Professor Trevor W. Hambley. His interests are in bioinorganic chemistry, described the complex reactions with endogenous the biological fate of metals in medicine, and spectroscopy in thiols that contribute to tumour resistance, and cellular and biological systems. their examination using NMR techniques. Matt Hall is the joint winner of the Platinum Metals Review While platinum drugs are the major research PGM8 conference student article competition.
liquid crystals could act as templates for the Tokyo, Japan) describing very effective asymmetric synthesis of heterogeneous metal catalysts based hydroformylation catalyst systems, and Eric Hope on mesoporous silicas. Jan Backvall (University of (University of Leicester, U.K.) showing how fluo- Stockholm, Sweden) demonstrated the use of roorganic groups can be exploited in green allenes as nucleophiles in palladium-catalysed cou- chemistry: to enhance the solubility of rhodium plmg reactions, and the emphasis of palladium and ruthenium complexes in supercriticalCOZ, and mediated C-C coupling reactions was continued also utilising fluorous phases themselves as super- by Hans de Vries (DSM Research, Geleen, The critical solvents. Netherlands) who presented thoughtful develop- More detailed fundamental studies relating to ments of Heck reactions. An alternative approach homogeneous catalytic processes were a feature of to C-C couplmg, namely hydroformlyation, was the programme. The elegant and penetrating stud- also stressed, with Kyoko Nozaki (University of ies of Bob Bergman (University of California,
Phtinmn Metah b.,2002,46, (4) 166 U.S.A.) provided great insight into C-H bond acti- gen bonds as q2-ligands. Richard Eisenberg vation processes, and Zhenyang Lin (Hong Kong (University of Rochester, U.S.A.) reported the University of Science and Technology) showed power of parahydrogen-induced polarisation to how theoretical studies can add to the insight in an track through the mechanistic pathways of Hz incisive way. Sylviane Sabo-Etienne (Laboratoire through a catalytic cycle, while Jon Iggo de Chimie de Coordination, Toulouse, France) (University of Liverpool, U.K.) reported on described the activation of boranes and silanes, impressive technical developments with a flow cell demonstrating the main group elements to hydro- to allow in situ NMR under hgh pressures, without
An Equilibrium in Catalyst Optimisation and Development? By G. R. Owen, Department of Chemistry, Imperial College, South Kensington, London SW7 2AY, U.K.
A number of the presentations at the Eighth mixture by recently developed nanotiltration tech- International Conference on the Chemistry of the niques. Careful choice of catalyst, the strong Platinum Group Metals focused on catalysis. One chelation of the pincer llgaflds in these cases, pre- of the major issues addressed was the cost involved vented catalyst leaching. in the design, synthesis and optimisation of new An important puzzle was also highlighted by catalysts. Why spend so much money and time on Professor P. S. Pregosin PTHZ, Switzerland) in his the preparation of expensive ligands and complicat- talk on the ‘meta-&&yl fleet’. This interesting ed techniques when mphenylphosphine with PdC12, contribution showed that greatly improved enan- under standard conditions, works well? tiomeric excesses are obtained when meta-dialkyl As the conference progressed through imagina- substituted ligands are used. The reasons for this tive and stimulating presentations it became cleat dramatic effect were discussed and studies have that the search for more efficient catalytic process- shown that in Pd-phospho-oxazoline ally1 com- es requires the involvement of both academia and plexes, the observed Cram-influence of both the N industry. While the optimisation of the processes and P donors were the same. This remarkable ‘heL can be left to the industrialist, academics should /i.g fleet’ dearly needs further investigation and may dedicate their time to design and enhancement of have many implications for reactivity. novel systems that might involve unprecedented The conference has shown that there is a great chemistry. deal of chemistry which is available for study, and There were a number of fascinating and inspii- in partidar platinum group metals can be used to ing presentations. Professor B. R James (University study a wide range of reactions. Pure curiosity and of British Columbia, Canada) provided an amusing application-driven research will continue to be advertisement for the paper industry, describingthe essential for the development of exciting and novel requirements for new strategies in the hydrogena- chemistry. In both cases, real investment will be tion of lignul found in wood pulp, particularly one required to achiwe the challenging aims ahead. using a RuCl~3H20and trioctylamine catalyst. This was a call to academia for some fresh ideas. The Author There were also some examples of novel routes Gareth Owen is working towards a Ph.D. in organometallic chemistry at Imperial College, under the supervision of Dr for the overall dwelopment of catalytic systems. Rambn Vilar. His thesis will concentrate on the palladium-mediated Two interesting presentations on the use of den- reactivity and insertion chemistry of carbon-heteroatom multiple bonds, such as isocyanides, imines and heterocumulenes. His drimer catalysts by the van Koten group (G. P. M. research interests include the design of novel supramolecular van Klink and R J. M. Klein Gebbmk, Utrecht ligands and their uses in the control of selectivity in catalysis. University, The Netherlands) were given. Organic Gareth Owen is the joint winner of the Platinum Metals Review products could be separated from the reaction PGM8 conference student article competition.
Pkztinum Metah Rev., 2002,46, (4) 167 the attendant problems of slow gas dissolution due It is unfair to the excellent contributed papers to poor mixing. This direct observation of homo- and to the poster presenters that I have concen- geneous catalysis, such as hydroformylation and trated on the contributions of the invited speakers. carbonylation, can be achieved under representa- In many ways they accentuated the perception that tive conditions. platinum metals chemistry is a mature, but still Although many of the complexes and materials youthful science, with new vistas opening. Indeed, describes above were ohgomeric and polymeric, that view was expressed by Helmut Werner in his few had direct metal-metal interactions. However, thanks to Giinter Schmid. The boundaries of plat- these were evident in the heterogeneous catalysts inum metals chemistry are still there to be probed described by Stan Golunski (Johnson Matthey, in a fundamental way, aided by the great array of U.K). He emphasised the ability of metals, espe- structural, spectroscopic, imaging and analytical cially palladium, to mediate the transfer of oxide techniques now available to us. ions from an oxide surface to a catalysis substrate. Indeed, the platinum group metals themselves Two talks, though, demonstrated differing but are now part of the array of analytical techniques, fascinating properties of nanoscopic metal struc- used for example in understanding the effects of tures; Phil Bartlett (University of Southampton, damage within DNA, and the capability for effec- U.K.) described how liquid crystals and solid tive functioning is continually being extended. microspheres (of polystyrene and silica) could be Ligand design and synthesis are developing apace, used as templates for the chemical and electro- and can be used to construct clefts at single metal chemical formation on mesoporous metals. These atoms, helicate grooves in oligomers, and complex materials provide large surface areas, like those of surfaces in dendrimers and polymers. As yet we do the nanoparticles in heterogeneous catalysts, but not understand these new structures well enough the area within is a concave, rather than a convex, to predict the applications in molecular electronics, surface and generates different types of metal sur- optoelectronics and catalysis. However, we can see face sites. It might also be expected that the large extended arrays of metal nanostructures that have arrays that comprise mesoporous metals may be a totally untapped potential. Perhaps even less do less prone to sintering than the clusters within a we understand how such complexes interact with hgh dispersion metal catalyst. So novel chemical living tissue. That they can do so to therapeutic applications of these materials in catalysis, electro- benefit is a major impetus to research. The confer- catalysis and sensors can be anticipated. ence demonstrated that the range of complexes The other approach was that of Giinter Schmid and materials that could be tested comprise a vast (University of Essen, Germany). His ligand-sta- array of types. And, as always, development of the bilised clusters lie at the boundary of molecular underlying theory of all of these interactions is complexes and colloids. The Au55 type of duster essential to orient further synthetic developments. with PPhs and the predominant protecang ltgand We are grateful for the organisation provided was reported to form 2-dimensional monolayers at by the Royal Society of Chemistry, and also to our a water-CHzClz boundary, and I-dimensional sponsors: Johnson Matthey, Synetix, BP Chemicals structures with different templates. A supramolec- and Nycomed Amersham. On behalf of the ular chemistry was established between these hgh National and Local Organising Committees, we nuclearity cluster materials. The electrical conduc- would like to thanks all of the attendees for a tivity across a single cluster molecule was also memorable scientific meeting. measured. In the junction to the nanoelectcodes, the ligand sheath acted as an insulating layer. The The Author metal core itself behaved as a coulomb well with John Evans is a Professor of Chemistry at the University of Southampton. His main interests are in surface organometallic properties attributable to quantum size effects, chemistry and heterogeneous catalysis, mechanisms of homogeneous catalysis reactions and X-ray absorption rather than being merely a segment of an extended spectroscopy. Professor Evans was awarded the Royal Society metal array. of Chemistry Tilden Medal in 1994.
pLATINUMmETALS rEV., 2002, 46, (4) 168 Structural Changes and Their Ianetics in Hydrogen-Containing Palladium Systems
By V. M. Avdjukhina, A. A. Katsnelson and G. P. Revkevich Department of Solid State Physics, Moscow State University, 117234 Moscow, Russia
Non-trivial structural changes and phase transformation kinetics have been found to occur in palladium-hydrogen and palladium-metal-hydrogen systems during relaxation processes as hydrogen is released. In the palladium-hydrogen system these changes take place in stages: an incubation period, a period of fast degassing, a period of stabilisation, and a post-stabilisation period. In palladium-metal-hydrogen systems the structural changes and phase transformations are non-monotonous (oscillating or stochastic). Time dependent kinetics have been observed over periods of up to tens of thousands of hours. An hypothesis based upon non-equilibrium thermodynamics and hydrogen interaction factors between matrix defects and atoms in the palladium systems is proposed to explain the phenomena.
The unique ability of palladium (Pd) to absorb est. These processes and their kinetics have been large quantities of hydrogen (H) was discovered examined in our research (4-12). about 130 years ago by Thomas Graham (1). The Stnkmg data obtained during our work show solution of H in Pd has a considerable effect on the important roles that the formation of defect the physical properties of the Pd (2,3); for exam- structure (at saturation) and its transformation ple, the Pd-H alloy is diamagnetic and super- (during degassmg) play. Thus the nature of the conducting, although Pd itself is strongly paramag- hydrogen effects on the structural changes in Pd-H netic. These differences are connected with the solutions and on the kinetics is significant. The atomic and electronic structural changes which mutual disorder in the distribution of Pd and other occur when H dissolves in Pd. Only atomic struc- metal atoms is an additional source of defect tural characteristicswill be considered here. structure formation. The most striking effects may Solid solutions of H in Pd correspond to 01- be expected in solutions where the metal is very phase regions if the atomic ratio of HPd, nH/npd, different to Pd - in terms of its affinity to hydro- is less than 0.024.03,and to P-phase regions if the gen. Some new characteristics of the structural nH/npd ratio is greater than - 0.60. When the ratio changes that appear when Pd systems are saturat- lies between these values, a mixture of both phas- ed with hydrogen can also be expected. Our results es is present. In both the 01- and P-phases, the Pd confirm that these structural changes are non- atoms form a f.c.c. structure, with H atoms occu- trivial (13-21). pying octahedral interstitial sites. The distance Characteristics of the structural changes in Pd between Pd atoms in the P-phase is - 3 per cent and some Pd-M alloys at saturation and during greater than in the a-phase, which is why the a H degassing will be considered here. X-ray tech- P phase transition process is accompanied by niques described elsewhere were used (1621). defect generation. The structural changes talung place in Pd-H during saturation with hydrogen and Samples and Methods of Investigation during degassing have become the subject of sys- Samples of Pd alloys were prepared by arc melt- tematic research. The changes occurring in the ing from highly pure (99.98Yo) elements in lattice and in the defect structure during the 01 + an argon atmosphere using a titanium getter, fol- P phase transition up to P saturation, and during lowed by annealing (for 24 h) at 900°C at a courses of P + degassing are of particular inter- pressure of lo* mm Hg to reach a homogenised
P/azinwm Metah h.,2002,46, (4), 169-176 169 time, see Figure 1 (7). Lines 1, 2 and 3 relate to regions or ‘blocks’ of coherent scattering ((hh’) 1 blocks) which have crystallographic planes with (loo), (311) and (110) indices, respectively, parallel to the external surfaces of the sample. n The experimental points lie straight lines - 15 on that do not pass through the coordinates (0,O). The - dependence of the P-phase concentration on time 3 00. is:
;;I -054 . P(4 = ’ - *[-rtt- fdl TIME, minutes I where y represents the logarithmic rate of P-phase Fig. I The logarithmic dependence of the Pphase growth and to represents the duration of the incu- concentration (p) in Pd on the hydrogen saturation time. bation period. Both y and to depend on the The lines relate to regions or ‘blocks’ (hkl blocks) of crystallographic orientation of the ‘block‘ planes coherent scattering with crystallographic planes. The initial incubation periods for the three blocks can be with respect to the external surface. The factor is seen before the lines begin. a maximum for the (100) blocks and a minimum Line 1 is for (100) blocks Line 2 is for (311)blocks for the (110) blocks, while to is a minimum for Line 3 is for (I 10) blocks (100) blocks and a maximum for (110) blocks. The dependence on orientation is considered to be state. After homogenisation, the samples were cut greater for y than for to. (using an electric spark method) into discs, 16-18 In addition, to and y depend upon the current mm in diameter and 0.2-5 mm thick. These were density,j. Asj increases up to 25 mA cm-’, the then ground and polished with diamond paste to a incubation period to decreases almost 40 times for mirror-like condition. The X-ray diffraction maxi- the (100) block while y increases by one order of ma of these samples were wider than for magnitude. These findings can be explained by the non-deformed samples. The grinding and polish- kinetic theory of first-order phase transformation ing had created a deformed surface layer to a depth (7). According to this theory, the P + a phase of > 10 pm (greater than the X-ray penetration transformation can take place when the decrease in depth (4 to 5 pm)). Samples were hydrogenated internal energy (due to a-phase formation) is electrolytically (740 minutes at a current density greater than the amount of energy needed to make of 2580 mA cm-’) in a bath of aqueous NaF boundaries between the new phase and the old solution (~?J’o) at room temperature. The sample one, to generate defects and to increase the elastic under investigation was made into an cathode, the energy of the matrix. (Elastic tension will appear anode was a Pt plate. Degassing was performed in because of differences in the specific volumes of air at room temperature. In some samples anneal- the phases). ing removed the effects of the deformation. During the a + p transformation, the effective Hydrogen saturation was attained after one pressure resulting from the saturating hydrogen, sequence or after repeated cycles of ‘saturation- (defined by the charging current density in the elec- degassing’ (cycling). trolyte bath) becomes part of a ‘thermodynamic stimulus’. The ‘embryos’ of the new phase at the a Peculiarities of Phase + P transformation are in plate form. Due to the Transformations in Pd-H increasing number of ‘embryos’ there is an energy Plots of the dependence of the P-phase con- loss linked to the elastic tension in the ma&, this centration p(t) in Pd on saturation times at low energy loss is anisotropic. The elastic energy asso- current density (2.5 mA cm”) show a logarithmic ciated with the appearance of the ‘embryo’ phases dependence between the In(1 - p) function and the reaches a minimum when their surfaces are parallel
Pkainwm Metah Rm, 2002,46, (4) 170 to the crystallographic (100) plane. The defect structure affects both the ‘thermo- 40. I I dynamic stimulus’ and the phase transformation I I I kinetics. Phase transformations occur by a sponta- I1 I”I neous movement of the boundary between the a- -? and P-phases (22). In fact, the rate of increase of ri the @phase concentration depends on the height lo- I I I of the energy barriers which have to be crossed I I 0- I I during migration of the a-crystal boundary (as a- I I I I I I 20 phase transforms into P-phase) (12). The defects, 0 5 10 15 I TIME, days which lead to irregularly distributed energy barriers of different heights, hamper movement and also Fig. 2 Dependence of the /%phase concentrution decrease the a + P transformation rate. The ener- on time for cycles I, 11, 111 and IV The arrows show gy of the interphase boundary migration reaches a that p changes at hydrogen saturation. In IV thejlut area of the initial incubation period can be seen minimum when the ‘embryo’ surface is parallel to the (100) crystallographic plane. The factors specified above explain the exis- 100, 1 tence of the ‘incubation’ period and its anisotropy. The value of to decreases as j increases, while to increases as the defect concentration increases and I 60 there is stronger anisotropy with the rate of new a 40 phase growth. Research to understand the factors involved in the structural changes duting the p + a transfor- I, . . , . , . .J mations was performed on annealed samples after 20 40 60 80 100 120 140 160 a single saturation and deformation, and on TIME, thousand hours annealed samples saturated with hydrogen by Fig. 3 Dependence of the /%phase concentration repeated cycling. on time afer the ninth hydrogen saturation for the (100)and (311) blocks. The incubation period is omitted but the other stages of degassing: the fast decrease in p Annealed Samples with a Swe Saturation concentration, stabilisution, and post-stabilisation with For a single saturation annealed sample, the oscillations in the /%phase concentration, can be seen P + a phase transformation (j= 40 mA cn-*, tSat= 15 min) began immediately after hydrogen Figure 3 shows the dependence of the P-phase saturation. During the first 25 hours the P-phase concentration, p(t), on time after nine saturations. content decreased 30 times (6). The first 5 hours Immediately after the ninth saturation the value of was the incubation period in the deformed sample. p(t) was 80 per cent; this value had been constant During the next 25 hours the P-phase concentra- over a period of 4000 hours. The P-phase concen- tion decreased 2.5 times and during the next 150 tration then decreased over 46,OOO hours. After this hours the P-phase decreased by up to 30 per cent time the P-phase concentration remained constant of its original value. for 50,000 hours, and then began to change again, The changes in P-phase concentration in an with oscillating behaviour. The p + a process annealed sample during saturation cycling are thus appears to have a ‘stage-like’ character. shown in Figures 2 and 3 (11). In Figure 2 the Unlike the 01 + p process, the P + a trans- incubation period is missing for the first three formation occurs spontaneously in air, although cycles. The degassing rate decreases as the number the initial stage is hampered by the defect structure of cycles increases. The incubation period appears that is already present. Further progress is influ- after the fourth saturation. enced by the generation of new defects and then
PIdimm Metah Rev., 2002,46, (4) 171 Fig. 4 The dependence .f ln(14,x/t2~w)on the relaxation time for Pd-11.3 at.% W alloy afrer the 47 third hydrogen saturation
.-EA c n -1.2 .- Ew - 1.6 e P - 2.0 r>r
0 10 20 30 40 TIME, days
0.4
0
00 31; -0.4 formations in the defect struc-
5 -0.8 ture. One of the characteristics of the transformation is the -1.2 growth of blocks in the (x- - 1.6 phase, which occur because regions of the dislocation wall migrate to block boundaries 50 60 70 80 90 TIME, days (11). As this process can occur in different parts of a sample at different rates, an additional by transformations that follow defect generation in irregularity appears in the system in the distribution the defect structure. An incubation period was of energy barriers in the a-phase crystals. This leads noticed after a single saturation only in a deformed to additional hampering of the interphase bound- sample, but was noted in annealed samples after aries, which stops p(t) decreasing. After the growth the fourth saturation. After nine saturations the of the blocks is completed the 'hampering factor' of incubation period became much longer following boundary migration should disappear. mechanical treatment of the surface because by The accumulation of defects and hydrogen at then the dislocation density had been increased. the boundaries of the block regions can lead to an Decreases in p(t) during the next stage of opposing process. This causes p(t) to change degassing show exponential characteristics only (oscillating character) and thus produce the next when the defect concentrationis not large. Increases stage of relaxation. The character of the structural in defect concentration,and the resulting creation of changes that take place at hydrogen saturation and complexes (vacancy complexes, dislocation walls) subsequent degassing seem to be closely related to lead to the appearance of lugher and wider energy the transformations simultaneously occurring in barriers in that region. Decreases in p(t) can be the defect structure. described by a power dependence or even by a log- arithmic function dependence on t, as postulated in Structural Changes in Pd-M-H (12). Any kind of time dependence (power or loga- Alloys and Their Time Dependence rithmic) relates to a transition to another kind of The unusual kinetics found for the structural defect. The transition to the next stage where p(t) changes caused by transformations in the defect stops changmg rmght correspond to specific trans- structure encouraged us to look at the kinetics of
Phrinwm Mekdr Rm, 2002,46, (4) 172 Fig. 5 Profiles of the X-ray diffraction maximum for Pd-8 at.% Er alloy, at 20, 130, 330 and 1300 minutes after n Initial state of saturation with hydrogen diffraction maximum
78 79 00 81 82 28, degrees
structural change in Pd-M-H alloys. Kinetic ening of the diffraction maxima and decreases in aspects of these structural changes have been their upper regions which occur every 4 to 5 weeks examined in Pd alloys with tungsten, W, (13-14), (the broadened diffraction maxima tvmgs' expand samarium (15), erbium, Er, (16-21), and in more so far that correct measurement is impossible). detail on annealed Pd-W (11.3 at.% W) and Quasi-periodicoscillations of the first type change deformed Pd-Er (8 at.% Er). The alloyhg ele- to stochastic oscillations after transition through a ments are characterised by their degree of affinity second-type structural change. to hydrogen. Tungsten has a lower affinity for The decrease in the In(I~/I~)function for the hydrogen than Pd, while Er has a %her affinity. first process can be caused by the appearance of In the equilibrium diagrams for these alloys, there defect regions of size 2-3 nm (25) and specific vol- is no P-phase region for a Pd-W alloy containing ume. Increases in the In(Im/Izm) function can be 11.3 at.% W, in fact, the Pd-11.3 at% W alloy is associated either with solutions of these regions or characterised by regions rich in W (2-3 nm in size) with the approach of their specific volumes to that (23), and by superfluous concentrations of vacan- of the matrix (defect disappearance). The width of cies (24). Pd-Er alloys (8 at.% Er) are also dose to oscillation of the difftaction maxima may be con- the solubility boundary. nected with the appearance and subsequent disintegration of dislocation loops of size 510 nm Palladium-Tungsten Alloys (25). The dependence of the intensities, In(b/Izo~), The appearance of oscillation in the structural on time in Pd-W doys is shown in Figure 4 after change after hydrogen saturation of the system the third saturation (Im and Izm are the normalised indicates that hydrogen-rich clusters have been intensities of the X-ray diffraction maxima for 400 formed in the Pd matrix. The specific volume of and 200, respectively) (1S14). The dependence these dusters is larger than that of the ma& and seems to be quasi-periodic as its character shows thus the dusters are not thermodynamically stable that two types of oscillations may be occurring in under normal conditions. For a 'non-contradicto- the system. The first oscillation is connected to the if model of this phenomenon it can be supposed structural changes which cause the quasi-periodic that stability will increase if the number of defects changes in the (i400/i200)function. During the ini- decreases - because superfluous vacancies diffuse tial stage, this oscillation has a period of - 7 days. into the hydrogen-enriched dusters. A lack of The second oscillation is connected to sa~ctural vacancies arising during this process in W-rich changes characterised by abrupt short-term broad- regions will be stimulated by contra-directed
Pkztinum Metals Ra.,2002, 46, (4) 173 model is, of course, an hypothesis and requires more direct proof. Nevertheless, it does describe the experimental data and may be used as the basis for a stricter model of the observed phenomena.
Palladium-Erbium AUoy The initial state in deformed Pd-8 at.% Er alloy (caused by grinding and polishing) is characterised by an essentially non-homogeneous distribution of the constituents and by a strong stretching tension (acting outwards to the surface) that acts perpen- dicularly to the surface. After hydrogen saturation the tension changes to compression. Maximum compression was reached two days after hydrogen saturation. After eight days the value of the com- pression had decreased by 25 per cent; then it remained practically constant for the next 1.5 years (17-18). 45 46 47 45 46 47 After hydrogen saturation the profile of the X- 2e, degrees ray diffraction maxima becomes doublets, see Fig. 6 Profiles of X-ray diffraction muxima for Figure 5. This indicates that two phases develop Pd-8 at.% Er alloy at various times after hydrogen that essentially differ from each other by the peri- saturation: (I) 1.5 hours, (2) 7 hours. (3)25 hours, (4)48 hours, od of the lattice. The time dependence of the (51 I20 hours, (6)4200 hours maximum profile has oscillating character, see Figure 6. Computer analysis of the profiles allowed vacancy diffusion; this will result in oscillation of us to determine the time dependencies of differ- the moving vacancies and will lead to first-type ences in Er concentrations in corresponding structural oscillation. After a few cycles, the vacan- phases and specific parts of these phases. The data cy concentration in the Pd-rich regions becomes in Figure 7 indicate that irregular oscillations (sto- so large that it would seem more advantageous to chastic) in the indicated characteristics have been form large vacancy dislocation loops during the occurring for 1.5 years. The oscillations occur in intermediate period (although these loops would the initial stage of degassing when there is 10-20 be unstable). The loops disintegrate soon after they per cent of H in the system and also in the later form, and then the process of defect cluster for- stages when the concentration of H is not more mation and disappearance begins again. This than 1 per cent (1S20). The data are explained
Fig 7 The dependence cfthe 04 I concentration of specific parts of 1.5 10 100 1000 10000 corresponding Er-rich phases in TIME, hours Pd-8 at.% Er alloy on time, after hydrogen saturation
PkafinnmMetah Rm, 2002,46, (4) 174 with a model which takes into account the micro- defect subsystems caused by the non-homoge- scopic theory of alloys and a synergy model. neous distributions of the metal and the associated The lattice compression found in the alloy afier non-homogeneous hydrogen distribution. hydrogen saturation can be caused by transforma- Hydrogen is captured by regions that have a hgh tion of the defect-metal (DM) complexes present bondmg energy for hydrogen and this keeps the in the alloy before saturation into hydrogen- system in a non-equilibrium state. This can lead to defect-metal (HDM) complexes because the several diffusion fluxes where ascendmg and gra- hydrogen-defect bond in Pd has hgher energy dient diffusions compete. (26). Thus, the HDM complexes have low specif- Such ‘static’ instability can transform the ic volume. As Er has a hgh affinity to hydrogen, dynamics to dynamics similar to those of Benard these complexes attract Er atoms and trap them. cells (27). Accordmg to alloy structure considera- They play a dual role, keeping the system in a non- tions, the oscillating character of the structural equilibrium state and allowing the appearance of changes can have different characteristics, indud- ascendmg diffusion. According to synergy consid- ing an alternating appearance and, in Pd-W-H, the erations, non-equilibrium conditions in the system disappearance of the defect regions. In Pd-Er-H permit oscillations connected to self-organisation the structural changes may also have the form of of the defect-structural states to appear (27). A stochastic phase transformations. competition between ascendmg diffusion and gra- The long-term oscillating structural changes in dient diffusion provides a mechanism which hydrogen-containing alloys correlate with changes allows any possible oscillations to be realised. in strength characteristics, for example, those in The various diffusion fluxes caused by the com- rolled steel (28). Further investigations of the petition in the two-phase system with the Er traps observed phenomenon will be to find Pd alloys in can cause oscillations in the phase transformation which it occurs and to examine its nature and any kinetics. The stochastic nature of these oscillations practical applications. Alloys Pd-Mo-H and Pd- may be related to differences in relaxation times of Ta-H alloys are now being studied. the different oscillation processes. Acknowledgement Conclusions This work has been supported by the Russian Fund of Fundamental Research, under grants Nos. 99-02-16135and 02- Structural changes peculiar to the hydrogen- 02-16537. containing systems Pd-H and Pd-M-H, where M is a metal having a different affinity for hydrogen to References Pd, have been considered. Non-trivial kinetics for 1 T. Graham, Phil. Trans. Rcy. Soc., 1866,156,399 2 P. Gel’d, R A. Rjabov and L. P. Mokhracheva, the CL transformation in Pd-H have been V. p -+ “Hydrogen and Physical Properties of Metals and found. The most important feature is the altemat- Alloys: Transition Metal Hydrides”, Nauka, ing stages in the P-phase concentration which may Moscow, 1985 or may not occur. This phenomenon is related to 3 “Hydrogen in Metals I”, eds. G. Alefeld and J. Volkl, Springer-Verlag, Berlq 1978 the influence of the origmal defect structure on the 4 A. A. Katsnelson, G.P. Revkevich, S. V. Sveshnikov transformation kinetics during the p + CL phase et al, Metakj$aa, 1985,7, (2), 66 transformation. The second important feature in 5 G. P. Revkwich, S. V. Sveshnikov and A. A. Katsnelson, I?. WZov,Fiz, 1988,31, (5), 102 the CL H p transformation is the strong depen- G. Revkevich, A. I. Olemskoi, A. A. Katsnelson dence of the associated p(t) function on the 6 P. and V. M. Khristov, Met&j$a, 1990,12, (3), 71 to orientation of the (hM) blocks relative the exter- 7 G. P. Revkevich, A. I. Olemskoi, A. A. Katsnelson nal surface. This is caused by the elastic energy and M. A. Knjazeva, MOJ~WUniv. Ply. BnL, 1992, dependence resulting from the orientation of the 33, (2), 74 8 G. P. Revkwich, A. I.’ Olemskoi, A A. Katsnelson plate formations. and M. A. Knjazeva, P~J.Met. Met., 1993,76, (l), 101 In Pd-M-H systems the kinetics of the structur- 9 A. A. Katsnelson, M. A. Knjazeva, A. I. Olemskoi al changes have oscillating character related to the and G. P. Revkevich, Sn~Invest., 1998,13,1443
P/acinrcm Metah Rev., 2002,46, (4) 175 10 A. A. Katsnelson, M. A. Knjazeva, A. I. Olemskoi 22 H. C. Jamieson, G. C. Weatherly and F. D. and G. P. Revkevich, Plys. Solid Stute, 1997,39, 0, Manchester,J. LwCommon. Met., 1976, 50, (l), 85 1275 23 S. A. Alimov and A. A. Katsnelson, Ply. Met. Met., 11 A. A. Katsnelson, M. A. Knjazeva, A. I. Olemskoi 1966,22,468 and G. P. Rwkevich, Mosmw Uniu. Plys. BwU, 1997, 24 A. A. Katsnelson and A. I. Olemskoi, “Microscopic 38, (6),46 Theory of Non-homogeneous Structures”, Mir 12 A. A. Katsnelson, M. A. Knjazeva and A. I. Publishers, Moscow, AIP, New Yo41990 Olemskoi, Ply. Solid Stute, 1999,41, (9), 1621 25 M. A. Krivoglaz, “Diffraction of X-Rays and 13 A. A. Katsnelson, A. I. Olemskoi, G. P. Revkevich Neutrons by Non-Ideal Crystals”, Naukova Dumka, and I. V. Suhorukova, Mosmw Ply. Bwll., 1994, Uniu. Kiev, 1983 35, (3). 68 14 A. A. Katsnelson, A. I. Olemskoi, G. P. Revkevich and 26 S. M. Myers, M. J. Baskes, H. K. Birnbaum et ul, Rev. I. V. Suhorukova,Ply&-U@kbi, 1995,165, (3), 331 Mod Pkys., 1992, 64, (2), 559 15 A. A. Katsnelson, G. P. Revkevich and V. M. 27 I. Pngogjne, “From Being to Becoming Time and Avdjukhina,Mosmw Uniu. Ply. BwU., 1997,38, (3), 68 Complexity in the Physical Sciences”, W. H. 16 V. M. Avdjukhina, A. A. Katsnelson and G. P. Freeman and Co., San Francisco, 1980 Revkevich, Sw$ Invest., 1999,14, (2), 30 28 V. M. Piskovets, T. K. Sergeeva, Yu. A. Bashnin and 17 V. M. Avdjukhina, A. A. Katsnelson, N. A. 0. V. Nosochenko, SteeI, 1994,(7), 60 Prokofjev and G. P. Revkevich, Mosmw Uniu. Phys. BwU, 1998,39, (2), 71 The Authors 18 V. M. Avdjukhina, A. A. Katsnelson and G. P. Valentina M. Avdjukhina is an Associate Professor of Physics at Revkevich, Ctyst. Rtp., 1999,44, (l), 49 Moscow State University. Her interests include X-ray diffraction crystallography, non-equilibrium systems, metal-hydrogen alloys 19 V. M. Avdjukhina, A. A. Katsnelson and G. P. and platinum metals. Revkevich, Momw Uniu. Pbs. BwU, 1999, 40, (5), 44 Albert A. Katsnelson is a Professor of Physics at Moscow State 20 V. M. Avdjukhina, L. Dabrowskii, A. A. Katsnelson, University. His interests include X-ray diffraction crystallography, J. Suvalskii, G. P. Revkevich and V. M. Khristov, non-equilibrium systems, metal-hydrogen alloys, the electronic Ply. SolidState, 1999,41, (9), 1532 theory of condensed matter, synergetics and platinum metals. 21 V. M. Avdjukhina, A. A. Katsnelson, D. A. Galina P. Revkevich is a Senior Scientist at Moscow State Olemskoi, A. I. Olemskoi and G. P. Revkevich, Ply. University. Her interests are X-ray diffraction crystallography, non- Met. Met., 1999, 88, (6), 576 equilibrium systems, metal-hydrogen alloys and platinum metals.
Polymer-Supported Rhodium Catalysts Soluble in SC-CO? In organic syntheses utilising homogeneous cat- The polymer was prepared by polymerisation of alysts, the catalysts are dissolved in a suitable the monomer lH,lH,2H,2H-heptadecafluorode- solvent which also acts as the reaction medium. cyl acrylate (zonyl TAN) and N-acrylosuccinimide These solvents are often toxic organic liquids, so (NASI); zonyl TAN increases the solubility in sc- there is a growing need to replace them with envi- COZwhile NASI provides attachment sites for the ronmentally benign solvents, such as water or catalyst. NH~(CH~)~PP~Z(DPPA) was then used to supercritical carbon dioxide (sc-COZ). At present, exchange the NASI groups in the polymer. Finally, the majority of organic syntheses are solvent-sensi- this was reacted with pulCl(COD)]z to obtain the tive and most homogeneous catalysts are not sc-COZsoluble, polymer-supported Rh catalyst. As soluble in either water or SC-CO~. the polymer is a very large molecule it was easily Separating and recovering the homogeneous separated by a membrane. catalysts at the end of the reaction is also a major Catalyst hydrogenation activity was evaluated problem. To overcome this, increasing attention is using 1 -0ctene and cyclohexene at different molar being directed at developing polymer-supported ratios of substrate:% and different temperatures. ligands for complexing with homogeneous metal Most reactions were performed at 173.4 bar pres- catalysts for straightforward membrane separation. sure for 12 hours. Conversion of I-octene to Researchers at Texas A & M University, U.S.A., n-octane was nearly 100%. Conversion of cyclo- have now succeeded in developing a homogeneous hexene increased 4th temperature: at 368 and 393 catalyst that is soluble in sc-COZ solvent (2.K. K, the maximum conversions were 39 and 51%, Lopez-Castillo, R Flores, I. Kani, J. P. Fackler and respectively. For this hydrogenation, the catalyst A. Akgerman, Ind Eng. Gem. Res., 2002, 41, (13), was Rh(TAN15DPPA)Cl with a Rh dimer:polymer 3075-3080). They did this by attaching a homoge- ratio of 1:3 and a Rh content of 1.95 mg of Rh/g neous rhodium (Rh) catalyst to the backbone of a of catalyst. The synthesis route for this Rh-polymer fluoroacrylate copolymer. catalyst is reproducible.
Plafnwm Metah Rev., 2002,46, (4) 176 9th International Platinum Symposium AN EXCHANGE OF INFORMATION AND IDEAS ON GEOLOGICAL AREAS OF PLATINUM GROUP ELEMENTS MINERALISATION
By R. G. Cawthorn Department of Geosciences, University of the Witwatersrand, PO Wits, 2050, South Africa
The geological community has been hosting demic interest, since at this stage they host no sig- International Platinum Symposia since 1971, the nificant grades above 1-2 g t-'. However, they first being held in Melbourne, Australia. Since then illustrate the type of host rocks in which minerali- Denver, U.S.A.; Pretoria, South Africa; Toronto, sation may occur, and the processes by which Canada; Espoo, Finland; Perth, Australia; mineralisation was concentrated. There are several Moscow, Russia; and Rustenburg, South Africa, rock associations that host PGE occurrences: have hosted the event at intervals of approximate- layered intrusions, concentric intrusions, brecciat- ly four years. Over the years the number of ed rocks related to intrusions, ophiolite complexes, delegates has increased by a factor of four (in exact komatiites, meteorite impacts, and alluvial proportion to the quantity of platinum group ele- deposits. ments (PGEs) mined and the price of platinum), Not mentioned at this meeting were the large with over 200 people attending the latest, the 9th tonnages, but very low-grade, occurrences found International Platinum Symposium, held in in mud rocks formed under oxygen-free condi- Bdhngs, Montana, U.S.A., in July 2002. The venue tions at the bottom of inland seas. However, in was conveniently placed for excursions to the these the grades are extremely low and it is unlike- Stillwater Complex, a classic layered intrusion ly that they will be exploited. These different hosting major palladium reserves, exposed in the settings and processes are briefly summarised. Beartooth Mountains in Montana. The delegates to these symposia come from Intrusions academic, exploration, mining and government Layered intrusions form from the slow coollng organisations, probably in that relative order in of large volumes of lava or (more precisely from its terms of numbers. At this meeang most areas of underground equivalent) magma. Layers of crystals the world were represented, with the exception of of different compositions (mainly of non-econom- Australia, which was rather surprising because con- ic minerals) are deposited by this process, and siderable exploration for PGEs is underway there. extensive thin, parallel layers form that can be eas- These meetings are primarily intended for the ily traced laterally. Examples, are the Bushveld exchange of geological information and ideas, with (South Africa), Stillwater (Montana) and Great less emphasis on mining, metallurgy, and extrac- Dyke (Zimbabwe) intrusions, that may have one or tion. Presentations generally range from docu- two highly PGE mineralised layers. In other cases mentation of exploration target areas, through the the underground magma did not form parallel lay- identification of assemblages of platinum group ers of rocks, but produced a pipe-like body wea minerals in different deposits, and geochemical volcanic feeder pipe), and each eruption produced information and techniques, to ideas on the gene- a discrete concentric cylinder of rock. Several such sis of such mineralisation and identification of PGE-bearing intrusions occur in the Urals in concepts aidmg future exploration programmes. Russia. Areas in which PGE mineralisation were doc- There is another potential zone of mineralisa- umented included the U.S.A., Canada, Brazil, tion in layered intrusions. The heat from such India, U.K., Finland, Russia, China, Zimbabwe and magmas causes melting of the underlying rocks South Affica, but many of these were only of aca- and reaction between the magma and the rocks in
Pl;lfnwn Met& Rm, 2002,46, (4), 177-1 80 177 the floor can cause mineralisation, especially of nickel, the tonnages and grades of PGEs, as mined nickel and copper, but PGEs may be a byproduct. in Canada and Western Australia, are relatively This mechanism has produced the major palladi- small. um reserves at Noril’sk in Russia. Igneous intrusions are always associated with Meteorite Impacts much heated groundwater (as seen in natural Early in earth’s history, numerous meteorites geysers). The steam can react with low-grade min- impacted the earth, and caused massive melting of eralised intrusions and concentrate the PGEs into the rocks on the surface. One such example, at hydrothermal (literally hot water) deposits. The Sudbury, Canada, produced a huge bowl-shaped steam and later intrusions permeate through, and mass of molten rock in an area where considerable break up the original rocks into fragments (called copper, nickel and PGE mineralisation was already breccias), and in that way can leach the PGEs from present. This mineralisation became concentrated the original rocks to deposit them in high-grade in the molten rock and eventually produced the areas. The Lac des Iles palladium-rich body in major deposits at the bottom of the bowl now Canada is such an example. being exploited at Sudbury.
Ophiolite Complexes Alluvial Deposits Lavas originate from deep inside the earth, in a Weathering of PGE-bearing rocks can produce part called the mantle, which lies at least 35 km secondary enrichment in the overlying soils or below the surface of the earth. Low concentrations river systems. The PGEs are extremely dense min- of PGEs occur in such mantle rocks. Usually these erals and also inert (not altered by surface rocks never reach the surface. However, where processes). Hence, they become concentrated in continents are crushed together in mountain-build- soils and rivers, while all the other minerals are ing events (such as the Himalayas, Alps, Rockies decomposed or washed away because of their and Urals) slices of mantle rock can be thrust up to lower densities. In this way a low-grade occurrence the surface. These rocks are called ophiolites and of PGE mineralisation may be upgraded in river are distinctive compared to surrounding rocks. systems. (Gold is also concentrated by this same They have been extensively explored since very process.) Such deposits are called alluvial deposits. minor concentrations of PGEs are found in them. The first platinum ever found, in South America, One of the characteristic rocks containing was concentrated by this process, but no high- PGEs in an ophiolite is chromite, and while these grade source rock has ever been found there. In bodies have been extensively investigated world- Russia considerable mining and exploration is wide, none has yet proved economic. The being undertaken for such occurrences. Since they continued interest in them possibly arises from the lie at the earth’s surface it is unlikely that enormous fact that the smgle largest resource of PGEs in the deposits have escaped detection by the prospec- world is a layer of chromite in the Bushveld tors’ pans. Complex (l), called the Upper Group 2 (UG-2) The statement that the PGEs are inert is not chi-omitite layer. absolutely correct. Under certain conditions extremely small concentrations can be dissolved in Komatiites very corrosive heated groundwater systems. These A relatively minor occurrence of PGEs lies at concentrations can then be deposited when the base of lava flows, especially extremely ancient the water cools or is neutralised by mixing lavas known as komatiites. In these settings, with fresh water. Clay minerals may adsorb molten lava has eroded a channel down the flanks the precipitating PGEs, and in ancient black of the volcano, and precipitated nickel-copper sul- mud-rocks in Europe extremely low concentra- fides in which the PGEs are a minor commodity. tions (totally uneconomic) of PGEs have been Although these bodies can contain high grades of reported. Qhs is the old Kupferschiefer, mined in
Plarinutn Met& Rm, 2002,46, (4) 178 central Europe for copper in the Middle Ages.) is the exploration of the enormous intrusion in Examples of all these rock types were docu- Duluth, Minnesota. This intrusion has been shown mented at the 9th Internetional Platinum to have very large quantities of mineralisation, Symposium, and several examples from different mainly of copper and nickel with minor PGEs, parts of the world were reported on for the first fairly near to the floor contact However, this min- time. In other cases, exploration programmes and eralisation is diffuse and variable in grade. academic studies on the origin and extent of Tonnages could be enormous, but grades are gen- known mineralisation were documented. There erally elusively low. Identification of specific are still many challenging aspects as to how eco- open-pit or underground mining targets is still nomic deposits of PGEs become concentrated, awaited. and exploration programmes are obviously influ- In Ontario and Minnesota, there are a number enced by such hypotheses, since each hypothesis of small intrusions, which have tantalising concen- makes certain predictions about what kinds of trations of PGEs. The general impression seems rocks, and especially their detailed chemical com- to be that broad zones (more than 10 m wide) of positions, are the best pathfinders or fingerprints mineralisation at 1.5 to 2 g f’might be amenable for mineralisation. For example, the PGE deposits to open-pit operations, but that thin (less than 2 m in the Merensky Reef and the UG-2 chromitite in wide), lqh-grade (Merensky Reef-style) minerali- the Bushveld Complex, the J-M Reef in Stillwater sation, accessible only by underground mining is and the Great Dyke, all occur in the middle of very not likely to be identified there. large layered intrusions. One school of thought is There was no mention at this meeting of some that the mineralisation rains downward from the other exploration regions. The Muskox intrusion overlying magma and accumulates into a layer of in the Canadian Arctic may have Duluth-style or crystals, like the well-known placer theory for gold Platreef-style (Bushveld) mineralisation (depend- mineralisation. An alternative view is that hot ing upon how bullish you want to be). In Australia, water systems dissolve the PGEs present in very there are also a number of layered intrusions in minor concentrations from low down in the intru- which PGE mineralisation is known and currently sion and precipitate the mineralisation in these being examined. reefs as the heated water percolates upward (like blotting paper suckmg spilt wine from a table- Extraction Challenges cloth). Exploration strategies would then differ, Exploration for PGEs has an inordinately long depending upon which process was considered lead time. One of the reasons is that the relative applicable in a certain area. proportions of the different PGEs can be very variable, and an extremely wide range of platinum New Areas of Exploration Activity group minerals might be present Given their By this stage readers are doubtless askrig exceptionally low abundance, determining the pro- whether there are any new areas of exploration portion of these minerals, and especially their activity that might lead to future economic intergrowth with various gangue minerals is chal- deposits. The answer is that there is probably lenging but fundamental to successful extraction. nothing very new. The exploration in Finland that It is this extremely complex relationship has been ongoing for twenty years has indicated between the different platinum group minerals multimillion ton resources in a few different intru- and the wide variety of gangue minerals that is sions and sew, and regional exploration is causing the apparent extraction problems encoun- probably evolving more to feasibility studies and tered by the Stillwater mines. The greater age of financial evaluation. Establishing continuity of the Stillwater intrusion and the subsequent events grades and extraction processes is now occupying that have faulted and altered the rocks and their centre stage. mineralogy, compared to the Bushveld Complex, Lagging somewhat behind the Finnish progress have caused mining and extraction problems. To
Platinum Met& Rm., 2002,46, (4) 179 the great relief of South African Bushveld mining to supply 80 to 90 per cent of the world’s platinum companies, no other area or example better typifies and palladium for the foreseeable future. the statement that ‘grade isn’t everythmg’. The 10th symposium in this series is expected It is for these reasons that many papers to take place in Finland in 2006. It will then be presented at the conference focused on documen- interesting to see how far towards viable commer- tation of the platinum group mineralogy in a great cial operation some of the sources mentioned at many different settings. Dealulg with grains, typi- the 9th symposium will have come. The confer- cally about 0.001 cm across, and present at grades ence website is www.platinumsymposiu.org. of 2 g t-’, is an extremely challenging occupation. Academic studies presented on such minerals pro- References vide information on how the PGEs could be 1 R P. Schouwstra, E. D. Kinloch and C. A. Lee, Phtimm Metals Rey., 2000, 44, (l), 33 initially concentrated in the rocks, and by contrast, 2 R G. Cawthorn, S.A@. J. Sci., 1999,95, (11/12),481 their counterparts in exploration are intent on get- ting them back out again! Addendum Geologically inclined readers may wish to obtain a recent sum- A Global Inventory mary of PGE deposits worldwide, “The Geology, Geochemistry, Mineralogy and Mineral Beneficiadon of The section above indicates that there are Platinum-Group Elements”, edited by L. J. Cab4 (Special unlikely to be any changes in worldwide PGE pro- Volume 54), Canadian Institute of Mining, Metallurgy and Petroleum, Montreal, 2002; website: www.cim.org. duction in the short term. In an address at the meeting, the Director of the U.S. Geological The Author Survey, Dr Charles G. Groat, had themes. His Grant Cawthorn is the Platinum Industry’s Professor of Igneous two Petrology at the University of the Witwatersrand. South Africa first observation was aimed largely at those people (E-mail: [email protected]).His main interests are researching the origin of layered intrusions and their varied who suggest that oil deposits are running out. He mineral deposits. pointed out that commodiues were not necessarily running out, it was simply that a global inventory was not available, but that with a global vlllage Recyclable Ruthenium-BINAP Catalysts mentality there would always be suppliers. Second, Ryoji Noyori has been involved in asymmetric and arising from this view, was the decision that homogeneous hydrogenation for over thty years. the U.S. Geological Survey would be conducting a His work in this important area has resulted in cat- a cooperative international global programme to alysts with hlgh selectivity and wide application (T. assess the undiscovered nonfuel mineral resources, J. Colacot, Pkdnum Metalr Rey., 2002,46, (2), 82-83). Among catalysts he has helped to develop is Ru- and that platinum would be among the fist group BINAP, (BINAP = 2,2‘-bis(dipheny1phosphino)- of commodities to be assessed. This plan is ambi- 1,l’-binaphthyl) which, as Ru(lI)-BINAP dihalide tious, and a comprehensive evaluation is expected complexes, provides a versatile general asymmetric to take seven to ten years. hydrogenation of functionalised ketones. writer feels that the fist conclusion should This Now, scientists from China have synthesised be applied with some caution to the platinum mar- dendridc Ru-BINAP catalysts that are peripherally ket. There is no other commodity in the world that alky-functionalised (G.-J. Deng, Q.-H. Fan, X.-M. remotely matches the PGEs for their uneven Chen, D.-S. Liu and A. S. C. Chan, Chem. Commun., worldwide distribution. However quickly new tai- 2002, (15), 1570-1571). These catalysts can be used gets are identified and brought to fruition, their for asymmetric hydrogenation in an ethanol/hexane contribution will be minor compared to the reaction medium. Acids: 2-arylacrylic, 2-phenyl- Bushveld Complex (2) and Noril‘sk areas. No acrylic and 2-[p(2-methylpropyl)phenyl]aciylicused other commodity is so dominated by so few sup- for model reactions had high catalytic activity and pliers. Given the reserve and resource figures enandoselectivity. Phase separation was induced by currently available, the Bushveld (mainly platinum) adding a small amount of water. The hexane cata- and Noril’sk (mainly palladium) areas will continue lyst-containinglayer can be removed for reuse.
Phtinum Mefah Rev., 2002,46, (4) 180 ACTTM Power CoatingsTM MULTIFUNCTIONAL INDUSTRIAL PLATINUM COATINGS FOR THE GLASS INDUSTRY
By Paul Williams Johnson Matthey Noble Metals, Orchard Road, Royston. Hertfordshire SG8 5HE. U.K
Almost every glass article in existence has been and oxidation resistance at elevated temperatures formed by cooling from a molten state (with the make it the ideal material for handlulg molten exception of the relatively tiny amount produced glass. Ideally, the entire glass-contact surface of a via sol-gel processing and similar routes). Molten glass furnace should be fabricated from platinum. glass is a difficult and challenging material to han- However, the hgh intrinsic value of platinum pre- dle due to the extremely high temperatures cludes this as an option for the majority of glass required to melt and combine the glass constit- producers. Therefore, this approach is confined to uents (typically 1400 to 1600°C) and to the hghly the hghest-value and extremely-specialist produc- corrosive nature of glass in this state. Further diffi- tion operations - that is, glass for flat panel display culties arise when glass is formed using automated screens or glass for lenses of extremely high-power production equipment. Over the last century or so astronomical telescopes. these difficulties have been overcome and mass- Instead, most sectors of the glass industry use produced bottles, windows, tableware and display platinum only for certain critically important items screens, amongst many other items, are now taken in the furnace. These items, protected by or manu- for granted. However, the various pieces of equip- factured from platinum, are subject to the most ment used to melt, distribute and form these glass corrosion or have the greatest effect on the quality articles all suffer from continual corrosion. The of the final product. In general, the extent to which corrosion causes two major problems: platinum is used in a furnace is determjned by a First, corrosion has an obvious limiting effect number of factors. These include the value of the on the lifetimes of the furnace and handling equip- product glass, the quality required of it and the cor- ment used to melt and process the glass. For rosiveness of the molten glass. For example, a instance, some of the furnaces that produce the single LCD glass production line uses about 350 kg more aggressive glasses (such as fluoride opal glass of platinum in the re-, distribution and form- for white tableware, or borosilicate glass for ing sections and typically lasts only 2 to 3 years. In Pyrex@articles and LCD screens) need to be com- this application, the use of platinum components is pletely rebuilt every two years and this can cost vital to the final product quality, and the high value tens of millions of pounds each time. of the product justifies the investment. By con- Second, the products of the corrosion process trast, the beer bottle plant mentioned earlier may (undissolved ceramic particles (‘stone’), chemical require only a few hundred grams of platinum for inhomogeneities (‘cord’) or bubbles (‘blister’)) can the thermocouples used to control the glass melt cause defects in the glass which reduce its overall temperature. The bottle production process would quality. While the occasional defect in a beer bot- certainly benefit from the use of platinum but it is tle may be of minor consequence, a single minute not a necessity for the final product and the hlgh- defect in a hgh-quality lead crystal item or LCD volume, low-margin nature of the business makes screen panel is completely unacceptable. using large amounts of platinum difficult to justify.
Materials for Glass Making Platinum Fabrications Platinum is one of the few materials that is rel- Traditionally, the platinum used in the glass atively immune from the corrosive effects of industry is either fabricated to produce solid, free- molten glass. Its hgh melting point (1769°C) (1) standing components or is wrapped (dad) around
PLdhm Metals Rev., 2002,46, (4), 181-187 181 ceramic or high melting-point metallic compo- below which the sheet is not sufficiently strong to nents. Both methods use rolled sheets of platinum support itself and contribute its protective and/or alloy (for example, 10%Rh/Pt or 20%Rh/Pt, mea- containment function. sured in wt.%o), which are cut, formed and welded to the requisite shape. Extremely complex and Platinum Coatings sophisticated fabrications can be achieved using An alternative technique, which utilises the ben- these processes. eficial properties of platinum in a far more efficient However, with such a precious resource, opti- manner, is by thermal spraying a protective plat- misation of its use is essential and in order to inum layer directly onto the glass-contacting minimise the amount of platinum the thicknesses surfaces of the production equipment. This of the platinum fabrications should be as small as process, known as advanced coating technology, possible. There is, however, a minimum thickness ACTTM(2), has the capability to render the
ACT^" Platinum Coatings ACPplatinum coatings are applied by a thermal spray deposition process. Platinum in wire or powder form is fed into an oxygen-propylene or plasma flame. The residence time within the heat source is carefully controlled to ensure that the platinum is melted without vaporising it. A com- pressed gas stream fires the molten droplets onto the surface to be coated. The droplets ‘splat’ on impact and solidify almost instantly. The large differential in thermal mass between the molten par- ticles and the substrate means that the component normally experiences ody a slight increase in temperature during the deposition process. A continuous feed of wire or powder ensures a uniform, even stream of thousands of droplets per second. Successive ‘splats’ build up to form the coating. The thermal spray gun is controlled by a sophisticated multi-axis robot. The precise control of speed and motion obtainable ensures that even, reproducible coatings can be achieved. Coatings are applied in a purpose built coating booth which collects any ‘over-spray’ platinum, thus minimising loss of metal. Correct preparation of the substrate material is vital to the integrity of the bond between sub- strate and coating. Great care is taken to ensure that the ceramic surface is in optimum condition to allow maximum adhesion of the coating. The substrate preparation methods allow the ceramic sur- face to be imperfect: minor defects can be rectified, but the number should be kept to a minimum.
The ACT‘Mplatinum deposition process is being used here to apply a thin layer of platinum to a fusion-cast ceramic block which will cover glass deliven, channels. Tlierniul spray techniques and sophisticnted robotic systems ensure that the distribution of the platinum coating matches the corefully designated coating profile:.for instance, two thicker (darker) bands of platinum can be wen on the upper surjiice
Phtitznm Mekrls Rm, 2002,46, (4) 182 The feeder chamber within u gltrs., production unit. The chamber comprise^ u 'T'-shaped cerumic tube through which the high temperuture molten glass flows from the melting urea to the forming machines. In this chumber a rotating and reciprocating screw-plunger moves stirring the glass und forcing it into the moulds. The feeder chamber is the part of the system that most requires protectioii from the corrosive eflect5 of the molten glass
coated component virtuaUy immune to the corro- sector of the glass industry that has traditionally sive effects of the molten glass. The process is used significant amounts of platinum in the pro- analogous to the cladding technique, where a base duction process. Over the last six years, the glass metal or ceramic component is protected by a plat- industry has progressively adopted ACTm coat- inum alloy sheet; however, the platinum is now ings as the standard production route. The best strongly and intimately bonded to the substrate examples of lead crystal tableware have always material. Rather than being a 'brick wrapped in been produced to stringent quality standards. metal foil', the component has become a compos- Recently, the growing trend for uncut or hghtly cut ite structure. The platinum coating provides the crystal has raised these standards even hgher. corrosion resistance at the surface, while the sub- Defects in the crystal are more apparent when strate material provides the bulk properties, there are fewer cuts made, so the defect tolerance mechanical strength and shape. As the substrate is much lower. In order to meet these high-quality now gives the system its strength, the platinum requirements, crystal manufacturers are increasing thickness can be reduced to the minimum required the number of platinum or platinum-protected to ensure an impervious barrier layer and hence parts in the production line, especially in the impart the necessary corrosion resistance. The delivery systems close to the forming zone. thickness of the coating is typically in the range of 200 to 300 pm, compared to a dad% thickness Delivery Systems of - 1 mm and above. The system that delivers the molten glass/crys- The obvious advantage offered by such coat- tal from the melting area to the forming machines ings is that far less platinum can be used than in is referred to as the feeder chamber. It normally the traditional fabrication or clad-ING techniques. comprises a ceramic ''I" shaped tube, the vertical This reduction in platinum requirement also section of which contains a rotating and recipro- makes it feasible to use platinum in positions and cating screw-plunger. This serves the dual function applications that would not normally justify the of homogenising the glass (stirring action) and investment of a fully dad platinum system. forcing the correct amount from the chamber into the moulds (plunging action). For high-quality Lead Crystal crystal production, the feeder chambers are either The effectiveness of the ACTm coatings can lined with platinum alloy dad-INGS or are ACTm be illustrated by their use in premium-quality lead platinum-coated on the internal surfaces. The crystal production. High-quality lead crystal is a quantity of precious metal required to do this is
PIninum Metah h.,2002, 46, (4) 183 Some Parameters of Platinum Materials Used in the Glass Industry
Material Melting point, 'C Density, g ~rn-~ Ultimate tensile strength (3) (fully annealed sheet), kg rnm-' Pt 1769 21.45 13 1O%Rh/Pt 1850 20.00 34 20% Rh/Pt 1900 18.72 49 I I I I obviously dependent on the size of the chamber. has recently cost more than twice as much (4). This Typically, about 6 to 7 kg of platinum-rhodium has a significant effect on the cost of a platinum- alloy is used for the clad option and 2.5 to 3 kg of rhodium alloy relative to pure platinum. However, platinum for the coated version. because ACTm coaangs utilise the ceramic sub- Pure platinum is rarely used for daddings or strate to provide the mechanical strength of the fabrications as it lacks the necessary strength when system, pure platinum can be used as the coating in the unalloyed condition. Therefore alloying material. additions are made to increase its strength. A com- If platinum protection of some form is not used, mon alloying addition for this purpose is rhodium, the molten glass will attack, corrode and dissolve normally at 10 or 20 per cent. Rhodium is normal- the ceramic of the chamber, thus limiting its life. ly considerably more expensive than platinum and The products of the corrosion process (stone, cord and/or blister) are swept into the forming moulds and manifest themselves as clearly visible defects in the hnal product. Consequently, hgh-quality lead crystal producers regard platinum as a vital part of their production process and other producers are increasingly using it too.
Heating Options The temperature of the glass/crystal as it is delivered to the forming moulds is a critical para- meter in the production process. The glass temperature must be carefully controlled to ensure optimum viscosity and the correct coolmg/solidi- fication rate. The last stage in the production process at which the temperature can be controlled is when the glass is in the feeder chamber. The temperature is then typically around 1000 to 120O0C, dependmg upon the size of the glass art- cle being produced and the actual glass/crystal composition. There are two main methods of maintaining and controllulg the temperature of the glass within the feeder chamber: Platinum Power CoatingsTMin a feeder chamber at Cwstulex (a tableware manufucturer in the Cxch One method that is used to maintain the tem- Republic) thot iA pmducing a stream of molten glass. The perature of the chamber, and hence the glass Jervo-controlled cutting 5hear.s are on either side of the gluss stream. In full-scale operution, the chumher inside, is by wrapping external electrical heating maintains u steady glass delivey temperature k 0.5"C elements around the outer walls of the ceramic.
Pkatimm Metah Rey., 2002,46, (4) 184 This form of heating is known as 'indirect heating'. The second method, commercially known as direct heated platinum systems (DHPS@) (5), uses free-standing platinum alloy tubes welded togeth- er to form the T' section feeder chamber described before. These tubes contain and distrib- ute the glass, and also control the temperature. Large electrical currents are passed through the platinum alloy, utilising the resistance/resistive heatmg effect to convert the electrical energy to heat. By using a control loop to adjust the current, the temperature can be precisely controlled. The reason that two very similar but funda- mentally different technologies continue to exist for this application is because each system has its own strengths and weaknesses and the crystal/ glass producers choose the version that best suits their partic& requirements. Schematic of an indirect1.y heated ACTTMcoated,feeder Indirect Heating of Platinum Clad Systems chamber. The coating provides full protection to the ceramic against glass corrosion. The temperature is An indirectly heated ceramic feeder system, controlled via Kanthal@ electrodes outside the ceramic clad with platinum (alloy), will enjoy the excellent bodv. Heat travels through the cerumic to reach the glass glass corrosion protection that platinum (alloy) offers. However, the chamber walls in the vertical amount of platinum to do so. It will also utilise section of the chamber can be subject to collapse platinum rather than platinum-rhodiumalloy. The due to suction from the viscous glass melt as the excellent bond between the coating and the sub- reciprocating screw-plunger makes the upward strate removes the danger of suction collapse. stroke. In order to combat this, the vertical section Grain growth within ACTm platinum coatings is could be strengthened, but to be effective the minimal (6) and due to the support of the ceramic amount of platinum (alloy) required would have to substrate is thus of much less consequence. be significantly increased. However, the heating method has the same limita- In addition, after prolonged exposure to the tions in temperature control as the clad version, high temperatures of glass forming, grain growth because in both these cases the heat source is on of the platinum (alloy) microstructure can weaken the outside of the ceramic. the mechanical strength of the material to such an extent that the chamber ruptures. Direct Heating of Free-Standing Platinum With this indirect heating configuration, the Fabrications response time is relatively slow as the heating ele- If the platinum dad+ or liner is directly heat- ments are on the outside of the ceramic and the ed, the component providmg the heating effect is heat has to be transmitted through the body of the in immediate contact with the glass. This results in ceramic chamber. This method does not give the a much more responsive system with an increased level of control that the direct heating option allows. level of temperature control. However, fabricated direct heating systems are Indirect Heating of Am."MPlatinum Coatings subject to the same mechanical issues as the indi- A ceramic feeder system that has been ACT* rectly heated dadded version: suction collapse, platinum coated will similarly enjoy excellent cor- large numbers of welds, grain growth, etc., and rosion resistance but will use a much smaller similar quantities of platinum-rhodium alloy will
Phhmm Metah Rev., 2002,46, (4) 185 also be needed. In practice, the choice is between just two of the above options. The majority of the indirect heating systems supplied to high-quality crystal producers are now ACTm coated rather than clad. However, within the industry, there are still manufacturers who continue to choose fabri- cated direct heating systems because they feel that the precise temperature control offered by this system outweighs the advantages of the coated system.
Power CoatingsTM Combining the Advantages Power Coatingsm were developed in order to provide the advantages of both systems and elimi- nate the drawbacks. Power CoatingsTM is a combination of the DHPS@ and ACTm coating technologies. An ACT^ platinum coating is applied to a ceramic substrate which is then direa- ly heated in the same manner as the solid platinum Schematic of a feeder chamber using Power Coatings" fabrications used in the traditional DHPS@ sys- protection. The ACT'M coating shields the ceramic from glass corrosion and also controls the glass temperature. tems. As well as providing the beneficial features The heating surface is in direct contact with the glass of both systems, it provides additional benefits thus giving a higher degree of temperature control such as increased responsiveness and hgh power capabilities. can be obtained over varying chamber dimensions. The temperature control achievable within a The heated coating is in direct contact with the chamber that has Power Coatingsm is extremely glass and its temperature is constantly monitored. precise. To monitor the temperature, thermocou- This provides a very responsive feedback loop that ples are embedded in the ceramic immediately allows accurate temperature control. Tolerances of adjacent to the coating. These supply accurate tem- k 0.5OC at operating temperature ranges of 1000 to perature data to the computer control loop that 1200°C are currently being achieved. automatically adjusts the power applied to the Accurate temperature control provides control coating, thus controlling the temperature. The over the viscosity of the molten glass. Having power applied is from a low voltage, high current accurate control of the glass viscosity, particularly (AC) source. The connection to the coating is at the point it is delivered to the moulding made via specially-designed power distribution machines, is a key benefit to an automated glass flanges which ensure an even current distribution manufacturer. For automated production, a critical around the chamber. operational parameter is the variance in the weight The temperature profile within the feeder itself of the discrete quantities of molten glass (gobs) can be specified by careful design of the coating that are delivered to the mouldmg machines to thickness over the interior of the chamber. The form individual glass articles. This parameter is heating effect of any section of the feeder chamber referred to as 'gob weight variance'. If the viscosi- will be determined by the resistance of the coating ty is under control then the gob weight can be in that section. The resistance is controlled by the controlled by careful regulation of the screw- geomeuy of the individual sections and by the plunger stroke. Ideally, the gob weight variance thickness of the applied coating. By careful variation should be as close to zero as possible. The variance of the coating thickness, a constant heating profile in gob weight that has been obtained with existing
Phtinum Metah Rev., 2002,46, (4) 186 A vie\\- looking dowri into LI Power Cocrtings" chamber during initid hear-up. No glass is present iri the chamber at this point: the jilow- is from the pltitinum conting. The chamber is running lit about 1200°C nnd this temperature was achieved with power being upplied on1.v to the coating. No other heot source was required
Power Coatingsm systems, such as that used by References Crystalex, No* Bor, Czech Republic, is less than 1 www.noble.matthey.com/pdfs/Engl1sh/37.pdf 0.2 per cent. This tightly-controlled delivery 2 D. R Coupland, Phtinwn Metah Rey., 1993,37, (2), 62;D. R Coupland, R B. McGrath,J. M. Evens and weight contributes towards the increased quality J. P. Hdey, ibid, 1995,39,(3), 98 of the product and to a reduction in the rejection 3 Takenfrom: rate by ensuring that the correct weight of glass is www.noble.matthey.com/product/detail.asp?id=2 consistently transferred to each mould, thus facili- 4 www.platinum.matthey.com/prices/ 5 www.eglass.de/ tating smooth, efficient operation of the glass 6 M. Doyle, P. Williams, D. Coupland and J. Jenner, forming machines. Znt. GbsI., 1999, auly-August), 102 There are now four standard designs of feeder chambers that use Power Coaqm. The cham- The Author Paul Williams is the Product Specialist for ACTTMcoatings and bers have volumes ranging from 8000 to 24,000 platinum fabrications for the glass industry at Johnson Matthey cm3and are able to deliver glass at temperatures Noble Metals, Royston. He has worked with the glass industry for up the last six years, was involved in developing Power Coatings"" to 1400°C. These chambers are suitable for deal- technology, and now Power Coatingsn and ACT" products. ing with the existing range of daily pull rates and gob weight delivery requirements for the vast Electrically Induced Phosphorescence majority of current indirectly and directly heated When the voltage applied to a poly(pam-phenylene) feeder systems. ladder-type polymer being tested for LED use was switched off, a team of researchers in Germany and Conclusion Austria (J. M. Lupton, A. Pogantsch, T. Piok, E. J. W. Glass technology is one of the oldest manufac- List, S. Pad and U. Scherf, Pbs. Rey. Lett.., 2002,89,(16), turing technologies. While using almost the same 167401) saw a long-lasting pink phosphorescent glow (h basic constituents now, as in the earliest times (for - 600 nm) instead of the expected, but shorter lasting, ornaments and utensils) the technology of produc- blue-green fluorescence (3L - 450 nm). Very low con- tion has advanced to the stage where manu- centrations (- 80 ppm) of Pd atoms left over from the facturers are able to produce perfect flat glass, process catalyst and bound to the polymer backbone are lenses and display screens. Modem developments thought to be responsible for this new effect. in the materials of production have contributed to Large numbers of dark long-lived triplet states gener- this advance, and with the efficiency and accuracy ated in the polymer by the electricalexcitation may diffuse available with Power Coaangsm technology, even thermally through the polymer fjlm until they encounter more predictable outcomes are possible. a Pd site where they decay as phosphorescence.
Platinum Metah b.,2002,46, (4) 187 ABSTRACTS of current literature on the platinum metals and their alloys PROPERTIES Liquid-Crystalline Materials Based on Rhodium Microstructure and Shape Memory Behavior of Carboxylate Coordination Polymers: Synthesis, Tisl.2(Pd27.0Ni21.8)and Tirs.s(Pdz8.sNi22.0)Thin Films Characterization and Mesomorphic Properties of T. SAWAGUCHI, M. SAT0 and A. ISHIDA, Muter sd. Eng., A, Tetra(alkoxybenzoato)dirhodium(ll) Complexes 2002,332, (1-2), 47-55 and Their Pyrazine Adducts Ti-rich (Ti51.z(Pdz7.,,Nizl.8))(1) and near-equiatomic M. RUSJAN, B. DONNIO, D. GUILLON and F. D. CUKIERNIK, ~i,p.5(Pd,.5Niu.o))thin films were annealed at 773, Chcm. Ma&., 2002,14, (4). 1564-1575 873 and 973 K from the amorphous state. At < 973 Rhz(x,y,x-BmOCn)4(B = benzoate group; m = nu- K, these crystallisations are effective for grain reline- ber of akoxy chains on the aromatic ring; X,J ? = ment. Film (l), annealed at 773 K, has line plate-like their anchoring positions; n = number of C atoms in TizPd-type precipitates with a diameter < 100 nm each akoxy chain) and their pyrazine adducts (with inside the B2 grain. The shape memory characteristics polymeric structure via connected metallic centres) can be improved by precipitate hardening. were synthesised. Most exhibit LC columnar and cubic mesophases with melting transition temperatures dose Hydrogen Absorption of Nanoscale Pd Particles to or below room temperature. The equatorial llgands Embedded in ZrOz Matrix Prepared from Zr-Pd of the adducts fdl the interdimeric space. Amorphous Alloys Piano-Stool Inversion in Arene Complexes of S. YAMAURA, K SASAMORI. H. KUILTRA, A. INOUE, Y.C. ZHANG andu.ARATA, J. Matm as., 2002,17, (6), 1329-1334 Ru(ll): Modelling the Transition State Nanoscale Pd panides in an isolated dispersed state T. J. GELDBACH, P. S. PREGOSIN and A. ALBINATI,]. Ckm.JOG., embedded in ZrO, matrix gave maximum Hz absorp- Dalton Trans., 2002, (12), 2419-2420 tion amounts of - 2.4 mass% (Hz/Pd) at 323 K and puH(yne)(Binap)]CF,SO, (arene = @-benzene 2.2 mass% (H*/Pd) at 423 K with Hz pressure of 1 (1) or -toluene) was prepared. The structures were h4Pa. In contrast, Pd metal in bulk and powder forms markedly distorted from a classical three-legged gave only 0.7 and 1.2 mass%, respectively. piano-stool structure with (1) having the P-Ru-P plane - perpendicular to the plane of the arene. The smucture of (1) indicates a transition state leading CHEMICAL COMPOUNDS from one diastereomer to another via inversion at Ru. Multinuclear Magnetic Resonance Studies of the Aqueous Products of the Complexes cis- and ELECTROCHEMISTRY trans-Pt(Ypy)z(N03)2Where Ypy = Pyridine Derivative Degradation Mechanism of Long Service Life F. D. ROCHON and c. TESSIER, Can. 1. Chem., 2002, 80, (4). 379-387 Ti/lrO2-Ta2O5 Oxide Anodes in Sulphuric Acid The product of the cis title complexes undergoing J. M. HU, H. M. MENG, J. Q. ZHANG and c. N. CAO, Corns. Sci., aquation in acidic pD was &~t(Ypy)~(DzO)z]~’, 2002,44, (S), 1655-1668 anodes whereas hydrolysis in basic medium gave cis- Ageing studies of Ti/700/, IrOz-30% tA2oS Pt(Ypy)z(OD)z. Complexes containing 2-picoline and over the whole of their electrolysis time in HzSO~ 2,4-luti&e ligands behaved differently in their 195Pt established that their performance can be divided into NMR due to the ottho effect. The trum analogues ‘active’, ‘stable’ and ‘deactive’ regions. In the first two stages, the loss of coated oxides is dominated by dis- showed two signals in acidic pD corresponding to the diaqua monomer and the monohydroxo-bridged aqua solution of the active component (IrOz exhibits dimer. Two species were also observed in basic pD. preferential loss). In the ‘deactive’ region, the oxide coatings are lost mainly by peeling at the Ti/oxide Nonradical Trapping Pathway for Reactions of layer interface region. Nitroxides with Rhodium Porphyrin Alkyls Bearing Preparation and Electrochemical Characterization PHydrogens and Subsequent Carbon-Carbon of Ti/Ru,Mnl-,O2 Electrodes Bond Activation J. L. FERNANDEZ. M. R. GENNERO DE CHIALVO and A. c. K w.MAK, s. K YEUNG and K. s. CHAN, Organometd’rcs,2002, CHIALVO,].j. APPL.E/e&uchem., 2002,32, (5), 51S520 21, (12), 2362-2364 DSA@type electrodes of Ru-Mn mixed oxides (30 I A novel nimxide-induced H atom abstraction and at.% Ru < 100) supported on Ti were prepared by p-elimination of Rh porphyrin alkyls was demonstrat- spray pyrolysis. Polarisation curves were used to eval- ed. Subsequent C-C bond activation of methyl- uate their behaviour as anodes for the Clz and 02 substituted nitroxides by the Rhoporphyrin radical evolution reactions. A composition of - 70 at.% Ru yielded Rh porphyrin methyl complexes. gave the best electrocatalytic activity and stability.
Plafinnm Metah b.,2002,46, (4), 18%191 188 PHOTOCONVERSION APPARATUS AND TECHNIQUE The Singlet-Triplet Energy Gap in Organic and Polysilicon Mesoscopic Wires Coated by Pd as Pt-Containing Phenylene Ethynylene Polymers High Sensitivity HPSensors and Monomers A. TIBUZZI, C. DI NATALE, A. D'AMICO, B. MARGESIN, S. BRIDA, A. KOHLER, J. S. WILSON, R. H. FRIEND, M. K. AL-SUTI, M. ZEN and G. SONCINI, sens. Actnutors B, Chem., 2002,83, M. s. KHAN.AGERHARD and H. B&LER,J. Ch.Ply., 2002, (1-3), 175-180 116, (21), 9457-9463 Mesoscopic poly-Si wires coated by a thin film of The evolution of the TI triplet excited state in a Pd (100 nm) can be used as HZ sensors. Using surface series of phenylene ethynylene polymers (1) and micromachintog combined with a usual microelec- monomers with Pt atoms in the polymer backbone tronic planar process, poly-Si wires of the following and in an analogous series of all-organic polymers (2) dimensions were fabricated 0.25-3.7 pm wide, with the Pt(lI) tributylphosphonium complex being 1OCL140 pm long, and - 600 nm thick. Because of replaced by phenylene was studied. The Pt increases their high surface/volume ratio, these wires exhibit a spin-rbit coupling so the TI state emission @hos- very hgh resistance percentage variation under HZ phorescence) is easier to detect. For both (1) and (2), absorption. the TI state was at a constant separation of 0.7 f 0.1 eV below the singlet .Y, state. CH4 Decomposition with a Pd-Ag Hydrogen- Permeating Membrane Reactor for Hydrogen The Effect of pH on the Emission and Absorption Production at Decreased Temperature Spectra of a Ruthenium Complex T. ISHIHARA, A. KAWAHARA. A. FUKUNAGA, H. NISHIGUCHI, J. c. ELLERBROCK, s. M. MCLOUGHLIN and A. I. BABA, Inotg. H. SHINKAI, M. MIYAKI and Y. TAKlTA, Ind Eng. Cbem. Res., Cbem. Commnn., 2002,5, (S), 555559 2002,41, (14), 3365-3369 The protonable ligand for the Ru(1,lO-phenanthro- The C& decomposition reaction into C and Hz line)~(3-carbethoxy,4-hydroxy-l,lO-phenanthioline)~+- over Ni/Si02 was investigated using a Pd-Ag Hz-per- (PF& complex (1) is readily prepared. (1) has a small meating membrane reactor. Removing the formed H2 spectrophotometric change that results in a large with the Pd-Ag membrane increases the CH, decom- emission intensity change. The emission intensity of position activity (> 88Yo) at < 773 K. A higher H2 (1) is pH dependent in the pH range S11. (1) is use- permeation rate was achieved with 77Pd-23Ag than ful for luminescence-based pH sensors. with 9OPd-lOAg, thus increasing CH, conversion. The Hz formed was > 99.99% pure. ELECTRODEPOSITION AND SURFACE COATINGS HETEROGENEOUS CATALYSIS Crystallographic and Electrical Properties of Deep Oxidation of VOC Mixtures with Platinum Platinum Film Grown by Chemical Vapor Deposition Supported on A1203/AI Monoliths Using (Methylcyclopentadienyl)trimethylplatinum N. BURGOS, M. PAULIS, M. M. ANTXUSTEGI and M. MONTES, Appr Cat& B: Envimn., 2002,38, (4). 251-258 M. HIRATANI. T. NmATAhlE, Y. MATSUI and S. KIMLTRA, Tbin Pt impregnated metallic monoliths (1) were pre- SoMFihs, 2002,410, (1-2), 2W204 pared from anodised foils. The catalytic oxidation Pt (1) grown by CVD using MeCpPtMe, Al thin films activity of (1) was tested for the VOCs: 2-propanol, were found to contain 0 and C impurities. The C toluene, methyl ethyl ketone, acetone and their mix- impurities produce a micrograin morphology that tures. Complete oxidation was achieved except for contributes to hgh residual resistivity. High 0 cont- 2-propanol, where acetone was found as an oxidation amination is observed, irrespective of the Oz/Ar ratio intermediate. Even if the adsorption of the VOC on during growth. The intrinsic electrical transport prop- the A203 is governed by its polarity, the reactivity is erty is not affected by the contaminants. (1) grown mainly affected by the competition of the 0 atoms under oxidative conditions have good electrical prop- chemisorbed on the Pt particles. erties so are useful as electrodes for MIM capacitors.
Electrodeposition of Osmium lsomerization and Hydrocracking of Mecane T. JONES, Met. Finfib..,2002,100, (6), 84,8690 over Bimetallic R-Pd Clusters Supported on The electrodeposition of 0sis reviewed. The &- Mesoporous MCM-41 Catalysts line process, hexachloro-osmate process, nitrosy1 s. P. ELANGOVAN, c. BISCHOF and M HARTMA", C&.! &ti., complex process and molten salt process are 2002,80, (1-2), 3540 described. Blackening of the 0sdeposit for the hexa- Pt-Pd/AlMCM-41 (1) is superior to Pt/AlMCM-41 chloro-osmate process is prevented by the use of dual and Pd/AlMCM-41 for n-decane isomerisation. The anodes inside and outside a large porous pot. Very use of (1) results in a &her Clo isomer yield at a sub- limited data on the deposit properties are available. stantially lower reaction temperature. (1) has a better Details of applications,alloys, analytical control tech- balance between the two catalytic functions, namely niques and toxicity are included. (19 Refs.) acid sites and metal sites.
Pkdinwn Metah h.,2002, 46, (4) 189 Laser-Activated Membrane Introduction Mass HOM 0 G EN EO US CATALYSIS Spectrometry for High-Throughput Evaluation of High-Throughput Screening Studies of Bulk Heterogeneous Catalysts Fiber-Supported Catalysts Leading to Room- A. NAYAR, R. LIU, R. J. ALLEN, M. J. MCCALL, R. R. WILLIS and Temperature Suzuki Coupling E. s. SMOTKIN, Anal. Cbem., 2002,74, (9), 193s1938 T. J. COLACOT, E. S. GORE and A. KUBER, otganometa&cx, 2002, LAMIMS has been used to evaluate catalysts such 21, (16), 3301-3304 as Pt/Ce02-ZrOz under realistic conditions. The cat- High-throughput screening of Ph3P-based poly- alyst array is supported on C paper overlaid upon a mer-supported catalysts such as FibreCatTM-l001 and silicone rubber membrane configuration in a varia- selected Pd/C catalysts gave nearly quantitative con- tion of MIMS. The C paper serves as a heat- version of activated and unactivated aryl bromides in dissipatinggas diffusion layer that allows laser heating Suzuki coupling using EtOH/H20. The FibreCat of catalyst samples to far above the decomposition catalysts did not leach Pd. Forpchloroacetophenone temperature of the polymer membrane that separates and 3-bromothiophene, coupling could be possible the array from the mass spectrometer vacuum cham- by tuning the FibreCat catalysts with t-Bu3P. ber. A bulk catalyst array spot can be evaluated for activity and selectivity in as little as 90 seconds. Palladium Catalyzed Oxidation of Monoterpenes: Catalytic Activity and Poisoning of Specific Sites Novel Oxidation of Myrcene with Dioxygen on Supported Metal Nanoparticles J. A. GoNCALVES, 0.w. HOWARTH and E. v. GuSEVSKAYA, J. Moi. Cutul. A: Cbem., 2002,185, (l-z), 97-104 s. SCHAUERMA", J. HOFFMA", V. JoH~QNEK, J. HARTMANN, Myrcene can J. LIBUDA and H.J. mmD,Angew. Cbem. Int. Ed,2002,41, C/-methyl-3-methylene-l,6-octadiene) (14), 2532-2535 be efficiently and selectively oxidised by O2 in glacial Molecular beam methods and time-resolved reflec- acetic acid containing LiC1, with PdC12-CuC12.New tion-absorption IR spectroscopy were combined in monoterpenes with a cyclopentane skeleton, 3- and order to investigate MeOH decomposition on Pd 4-(1 -acetoy-1-methylethyl)-1 -vinylcyclopentene, were nanoparticles/Alz03/NiAl(l 10) model catalyst. Two produced. These products have a pleasant scent with competing reaction pathways were observed: a rapid a flower or fruit tinge and have potential as compo- dehydrogenation to give CO and a slow C-O bond nents of synthetic perfumes. breakage to form C and hydrocarbon species. It was shown that C-0 bond breakage occurs preferentially Novel Synthesis of Fused lsoxazolidines via a at particle step and edge sites. Palladium Catalysed Allene Insertion-Intramolecular 1,3-Dipolar Cycloaddition Cascade Reaction Hydrogenation of Phenol by the Pd/Mg and Pd/Fe T. AFTAB, R. GRIGG, M. LADLOW, v. SRIDHARAN and Bimetallic Systems under Mild Reaction M. THORNTON-PETT, Cbm. Commun., 2002, (16), 175L1755 Conditions Aryl iodides react with allene (1 am) and nitrone in J. MORALES, R. HUTCHESON, c. NORADOUN and I. F. CHENG, toluene at 120°C over 48 h in the presence of 10 Ind Eng. Chem. Rcs., 2002,41, (13), 3071-3074 mol% Pd(OAc)2, 20 mol% PPh3 and CSZCO~to Three Pd-catalysed zerovalent metal systems were afford the correspondmg isoxazolidines in 5&77% able to hydrogenate phenol to cyclohexanol and yield. The synthesis is a one pot reaction involving a cyclohexanone at room temperature and pressure. Pd catalysed allenation of the aryl iodide in combina- Treatment of aqueous phenol solutions (5.0 mM) tion with a nitrone cycloaddition, creating two rings, with Pd (2.6 ppt m/m)/Mg (1.00 g 20 mesh) and with two stereocentres and one tetrasubstituted C centre. 0.53 g of 1/8 in. Pd (0.5%)/&0, in contact with 1.00 g 20 mesh Mg resulted in 74% and 24% destruc- Polymerization of Phenylacetylene Catalyzed by tion, respectively, of the reactant after 6 h. The Pd/AL,O, Diphosphinopalladium(l1) Complexes with Mg system was greatly enhanced by 2% v/v K LI, G. WEI, J. DARKWA and s. K. POLLACK, Mammokmh, glacial acetic acid, resulting in an 84% reduction of 2002,35, (12), 457-576 phenol with a C balance of 93%. Cationic bis@hosphino)Pd complexes were gener- ated in situ by the reaction of (dppQPdCl(CH3), Self-Regeneration of a Pd-Perovskite Catalyst for (dippf)PdCl(CH3), (dppe)PdCl(CHj), (dppf)PdCL, Automotive Emissions Control (dippQPdC1, and (dppe)PdCl, (dppf = bis(dipheny1- Y. NISHIHATA, J. MIZUKI, T. AKAO, H. TANAKA, M. UENISHI, phosphino)ferrocene, dippf = bis(diisopropy1phos- u KIMURA,T. OKAMOTO and N. HAMADA, Nutun, 2002,418, phino)ferrocene and dppe = bis(dipheny1phosphino)- (6894), 16L167 ethane) with AgOTf. The dppf- and dippf-Pd com- X-Ray diffraction and absorption established that plexes catalysed the polymerisation of phenyl- I~F~s-/C~n.tnPdonsO~autocatalyst (1) retains hgh metal acetylene, whereas the dppe analogues formed phenyl- dispersion owing to structutal responses to the fluctua- acetylene ohgomers. The htghest molecular weight tions in exhaust gas composition. As (1) is cycled polymer was obtained from a 1:l CHzCIz/CH,CN between oxidative and reductive atmospheres, Pd mixture at room temperature. This seemed to be the reversibly moves into and out of the perovskite lattice. best conditions for polymerisation.
Phfin#m MetaLF Rev., 2002, 46, (4) 190 A Simple, Recyclable, Polymer-Supported FUEL CELLS Palladium Catalyst for Suzuki Coupling - Fundamental Aspects in Electrocatalysis: An Effective Way to Minimize Palladium from the Reactivity of Single-Crystals to Fuel Cell Contamination Electrocatalysts w.-c.SHIEH, R. SHEKHAR, T. BLACKLOCK and A. TEDESCO, K. A. FRIEDRICH, K. P. GEYZERS, A. J. DICKINSON and Syntb. Commnn., 2002,32,(7), 1059-1067 u. STIMMING,J. EkmdCbm., 2002,526525,261-272 Preparation of a polymer-supported catalyst (1) Nanostructured Pt-Ru electrodes prepared by metal involved wet impregnation of a polymer-bound electrodeposition exhibited distinct characteristics phosphine with PdClz in EtOH. (1) was used for regardmg CO oxidation due to a cooperative reaction Suzuki coupling. After each cycle (1) was recyclable mechanism involving CO surface mobility. For Pt- with low Pd leaching. The Suzuki coupling of an aryl- Ru/C catalyst, prepared by the sulfito method, at bromide with ptrifluoromethylphenylboronic acid 25°C the mass activity increases with increasing cata- resulted in the synthesis of 2-aminotetralin, used in lyst mass loading I - 55 wt.%. Then a plateau in the the treatment of epilepsy, stroke, and brain or spinal mass activity vs. weight loading is reached. At 65"C, a trauma. maximum mass activity occurs at 60 wt.%.
1,3-Dipolar Cycloaddition Reactions of Carbonyl Surface Properties and Physicochemical Ylides with 1,2-Diones: Synthesis of Novel Spiro Characterizations of a New Type of Anode Material, Oxabicycles La,_,Sr,Cr,_,Ru,OJ_s, for a Solid Oxide Fuel Cell v. NAIR, K. c. SHEELA,D. SETHUMADHAVAN, R DHANYA and under Methane at Intermediate Temperature N. P. MTH, Tetrabednm, 2002,58, (21), 41714177 A.-L. SAUVET, J. FOULETIER, F. GAILLARD and M. PRIMET, A facile 1,3-dipolar cydoaddition reaction of car- J. CataL, 2002,209, (l),2534 bony1 ylides with a range of 0-quinones afforded The material Lal_~rxCrl_yRuyO~_g(1) gave no loss highly oxygenated spiro oxabicydes. RhZ(0Ac)Z was of Ru even after sintering in air at 1100°C. The activ- employed as the catalyst. The reactions were carried ity of (1) for CH, steam reforming in a CH,-rich out in toluene at room temperature under atmos- an atmosphere is similar to that of Ru metal. However, phere of Ar. For 1,2-benzoquinones, the ylide Ru loss during prehmary treatment and the agglom- preferentially adds to the more electron deficient of eration of Ru particles during reaction were avoided. the two carbonyls of the quinone.
A Free Ligand for the Asymmetric Dihydroxylation ELECTRICAL AND ELECTRONIC of Olefins Utilizing One-Phase Catalysis and ENGINEERING Two-Phase Separation Effects of Si Interlayer Conditions on Platinum Y.-Q KUANG, s.-Y.ZHANG, R.JIANG and L-L. WEI, Tehbednm Ohmic Contacts for p-Type Silicon Carbide Lett., 2002,43, (20), 3669-3671 T.JANG, J. w. ERICKSON and L. M PORTER, J. Ekctmn. Muter., A free bis-cinchona alkaloid derivative (1) was used 2002,31, (5), 506-511 as the hgand in the 0s-catalysed asymmetric dihy- A study of Pt ohmic contacts with Si interlayers on droxylation of olefins. (1) can be easily prepared. The ptype Sic was performed. The use of a Si layer molar ratio of (l)/olefh was 5%, which was much decreased the specific contact resistance (SCR) rela- lower than that required for the corresponding solu- tive to Pt contacts without Si. The SCR values were ble polymer-supported cinchona alkaloid ligands reduced further by: (a) the deposition of the Si layer (1&25%). Yields of 89-93% and ees of 89-99% at 500"C, @) the incorporation of B in the layer, and were achieved with (1). Repetitive use of (1) is possi- (c) the design of the PtSi layer thicknesses in a 1:l ble without significant loss of enantioselectivity when atomic ratio. The lowest average SCR value was 2.89 a small quantity of OsO4 is added after each run. x 10-4R cm'.
The Oxidation of Alcohols in Substituted Structural and Magnetic Properties of CoCrPt lmidazolium Ionic Liquids Using Ruthenium Perpendicular Media Grown on Different Buffer Catalysts layers V. FARMERandT. WELTON, Green chin., 2002,4, (2),97-102 C. L. PLAlT, K. W. WIERMAN, E. B. SVEDBERG, T. J. KLEMMER, Substituted imidazolium ionic liquids may be used J. K. HOWARD and D. J. SMITH, J. Map. Map. Muter., 2002, as solvents for the oxidation of alcohols to aldehydes 247, (2), 153-1 58 and ketones using ["PrqPuO,] (1) as the source of Thin buffer layers (- 10-15 nm) of Ta/Ru, Ta/Hf the metal catalyst. (1) was used in conjunction with or amorphous (CoCrPt)Tau for growing CoCrPt film either N-methylmorpholine-AJ-oxideor 02 as co- on gave media layers with high perpendicular coerav- oxidants. Benzylic alcohols were oxidised to their ity (- 3 kOe). Coercivity was only 1.7 kOe with a aldehydes in good to excellent yields, whereas aliphat- Ta/Ti buffer. XRD rocking curves showed the highest ic alcohols required much longer reaction times and degree of (0 0 0 2) texture with the Ta/Ru buffer. This gave poor yields. buffer promoted local epitaxy with the media layer.
Pkdinm Metah b.,2002,46, (4) 191 NEW PATENTS EL ECTR 0 DEPOSITI 0 N AN D S U R FACE Colouring Mater SensitisationType Solar Battery Cell DAINIPPONPRINTING Japanese AppL 2002/093,475 COATINGS A colouring matter sensitisation-type solar battery Film Deposition on Nanometre Structures cell is made from laminations of a transparent sub- IBM COW US.AppL 2002/0,090,458 strate, a mansparent electrode layer, a power generation Thin film is deposited on a nanometre structure layer, a back electrode layer and a back substrate. The without filling holes and trenches by coating with a back substrate is pattern-coated with a Pt paste to aerogel material and a metallic seed layer, such as Pt form the back electrode layer, then baked with a or Pd acetylacetonate. The coating is combined with coating liquid of 6ne TiOz grains to form an oxide a supercritical fluid, such as sc-CO2, and a co-solvent, semiconductor film. The hlm is impregnated, dried, such as an alcohol. When the supercritical fluid is and carries a Ru complex pigment sensitiser. Highly removed the coating solidifies into the thin solid film. efficient power generation is obtained.
Chemical Vapour Deposition of Ruthenium Films Hydrogen Separating Membrane APPLIED MATERIALS INC U.S. Patent 6,440,495 MITSUBISHI KAKOKI K Japanese Appl. 2002/119,834 A method to deposit Ru 6lms via liquid source The manufacture of a highly permeable HZ separat- CVD uses vaporised bis(ethylcyclopentadieny1)Ru as ing membrane (1) for separating HZ from a H2- the CVD source material gas at 100-300°C in a reac- containing gas is claimed. (1) is made by forming a tion chamber. An 02source reactant gas is provided. Pd-based thin film on the surface of a porous carrier, The substrate comprises Ti nitride, TiAl nitride or Ta and then depositing a Pd alloy or a metal to be pentoxide at a temperature of - 100-500°C and has alloyed with Pd on the pinhole parts of the mem- a seed layer of Ru, Ir, Pt, Ru oxide, Ir oxide, etc., on brane. After heat treatment, when a Pd-metal alloy is which the Ru films are formed. The Ru film can be formed, the pinholes are effectively closed, and HZ used as an electrode in a MIM capacitor. yield is increased. (1) is easily made.
APPARATUS AND TECHNIQUE HETE R 0 G EN EO US CATALYSIS Thin Film Oxygen Sensor Ruthenium Perovskite Production PANAMETRlCS INC WorkiAppL 02/42,?56 NATL INST. MATER SCI. Eumpean AppC. 1,233,002 An Oz sensor operating at 30&350"C, comprises a Ru perovskites of the type L&UO, (1) are pro- crystalline Zr02 (1) sheet, and two porous Pt elec- duced by reacting an aqueous solution of La and Ru trodes poisoned by Pb to a level that will inhibit cross ions with a precipitate-forming liquid to coprecipitate sensitivity to reactive components, such as Hz. The Pt hydroxides of La and Ru which are then heat treated. electrodes are arranged to induce superionic 0 trans- (1) may also be precipitated onto a carrier from a port along current paths in (1) at the electrode homogeneous solution containing La, Ru and urea. surface. Oz concentrations of ppb can be detected. The coprecipitated hydroxides have uniform disper- sion and the resulting materials are efficient catalysts. Optical Switching Device US.PHILIPS CORP U.S.epl. 2002/0,089,?32 Destruction of CO, VOC and Organic Emissions An optical switching device comprises a transparent DEGUSSA AG WorkiAppL 02/34,371 substrate and a switching film of a hydride of Sc and A hgh performance catalyst (1) for the destruction Mg, and optionally Ni, Al, Cr, etc., covered with a Pd of gaseous CO, VOC and halogenated organic emis- or Pt catalytically active layer, in contact with an elec- sions comprises a layer of Pt group metal deposited trolyte. When a potential or current is applied on an inert support. A washcoat into which the Pt is between two electrodes, a change in optical transmis- deposited consists of Alz03 stabilised with LazO3, sion is detectable. The hydride is electrochemically CeOz stabilised with ZrOz and Pr'OIl. (1) is promot- switched from a low-H, mirror-like composition to a ed by S-containing compounds selected from Ptso3, high-H, transparent composition, and vice versa, by HzS04,(N&)zSO4, TiOS04,Ti2(S04)3, etc. H exchange. The device can be used in an optical switching element or sunroof. Production of High Quality Oil Bases INST.FRANCAIS DU PETROL WoriiAppLr. 02/48,289-290 Electrochemical Light-Emitting Elements The simultaneous production of very high quality SHOWA DENKO KK Japanese &L 2002/0?5,001 oil bases and middle distillates comprises successive An electrochemical light-emitting element (1) uses a steps of hydroisomerisation (1) and catalytic dewax- Ru complex for its hght-emitting layer together with a ing (2). (1) is performed in the presence of a Pt group high-polymer solid electrolyteand an electrolytesalt (1) metal catalyst deposited on an amorphous acid SiOz- has a hlgh performance and needs only a low driving &03 support, with metal dispersion of - 20-100%. voltage to produce hlgh ltght emission. (1) has superior (2) occurs in the presence of a Pt or Pd catalyst and a stability, reliability, and low manufacturing costs. molecular sieve selected from ZBM-30, etc.
Phiitzum Metah Rev., 2002,46, (4), 192-194 192 Catalytic Converter for a lean-Burn Engine H 0 M0 G E NEO US CATALYSIS JOHNSON MAlTHEY PLC U.S. Patent 6,413,483 catalytic converter (1) for a lean-bum engine C-C Coupling Reaction A DSM NV Worki&L 02/57,199 comprises a supported two-layer catalyst. The first A C-C coupling reaction between an optionally layer contains Pt, K and a Ba NOx storage compo- substituted (hetero) aromatic bromide compound (1) nent on a washcoat of a mixture of at least two of and a second reactant, such as an aryl boric acid is Alz03, CeOzand/or ZrO,. The second layer contains claimed. The process was performed in the presence Rh on a washcoat of CeOz and ZrOz. (1) further has of an aprotic dipolar solvent, such as dimethylfor- an interlayer of a Ba compound on a washcoat. (1) is mamide or N-methylpyrrolidinone, a base and a Pd more selective for catalytic reaction between NOx salt catalyst. The ratio between the quantity of Pd and/or nitrate with hydrocarbons and/or CO than present in the Pd salt and (1) is 0.00001~.1molYo, for between hydrocarbons and/or CO with 02. NOx preferably 0.014.1 molYo. (1) should contain at least can be reduced to Nz under constant lean to stoichio- one heteroatom chosen from N, 0 and S. metric conditions without the need for rich spikes. Acetic Acid and Methyl Acetate Production Hydrogenation of Acetylenes ACETEX CHIMIE WwklAppL 02/62,739 UOP LLC U.S. Patent 6,417,419 A continuous production of acetic acid and/or Hydrogenation of 4C acetylenes in a liquid hydro- methyl acetate, based on carbonylation of MeOH, carbon stream that contains mainly butadiene is dimethylether, etc., is performed in a homogeneous performed by contacting H2 and the hydrocarbon liquid phase under CO. The catalytic system com- stream with B catalytic composite on an inorganic prises Rh and a halogenated promoter, with HzO at oxide support. The catalytic composite has an aver- > 14?h concentration. The process is gradually mod- age, diameter of 5 800 p,with 2 70 wt% of Cu and ified by adding an Ir compound. The system shifts actlvator metal Pt, Pd, Ni, Co, Mn, or their mixture, from being a Rt-based homogeneous catalyst on its being finally dispersed on the outer 200 pxn layer of own to a catalyst based on Rh and Ir, or even Ir the support. The microsphere catalyst has much alone, without stopping the installation and reducing improved stability and selectivity compared to similar the H20content. catalysts with particles of diameter - 1600 p. Ruthenium Alkylidene Catalysts for Olefin Metathesis Vapour Phase Carbonylation with Iridium and Gold WFORNLA INST. TECHNOL. U.S.Pafmt 6,426,419 EASTMAK CHEMICAL co U.S.Patent 6,441,222 Ru alkylidene complexes (PCy3)(L)CIzRu(CHPh) A vapour phase carbonylation process produces (l),where L is a triazolylidene ligand, are claimed. (1) carboxylic acids and esters from a gaseous mixture of show hgh olefin metathesis activity, which is much lower aliphatic alcohols, ethers, esters, CO and ester- higher at lugher temperatures than that of the parent alcohol mixtures using a solid supported catalyst. The catalyst (FCy3)2C12Ru(CHPh)(2). When L is 1,3,4 gaseous mixture includes a halide promoter, and also aiphenyl-4,5-dihydro-lH-triazol-5-ylidene,(1) is able HzO and MeOH in a molar ratio of - 0.01:l to - 1:l. to catalyse the ringclosing metathesis of substituted The catalyst may be C, activated C, pumice, AlzO3, dienes to give tetrasubstituted cyclic olefins in good etc., containing 0.01-10 wt% of Ir and Au each, yield. Additionally, (1) has a similar stability towards preferably 0.1-2 wt.%. The catalyst also comprises Oz and moisture as that exhibited by (2). another metal selected from alkaline metals, alkaline earth metals, Sn, etc. The carbonylationis performed living Radical Polymerisation Initiator at 100-350°C and a pressure of 1-50 bar absolute. KURARAY CO LTD Japanese AppA 2002/080,523 A living radical polymerisation initiating system (S)-1-Phenylpropylamine applicable to a wide range of radically polymerisable TOYO KASEI KOGYO Japanese &pL2002/088,031 monomers comprises a halogenopentamethyl cyclo- (.li-l-Phenylpropylamine (1) is prepared by reacting pentadienyl bis(miary1phosphine) Ru, an a-halogeno- (R)-1 -phenylpropyl alcohol with diphenylphosphoryl carbonyl compound or a-halogenocarboxylic acid azide as an azidation agent in the presence of a base ester, and an amine. The system can easily and quick- to provide (4-l-phenylpropyl azide (2). (2) is then ly produce a polymer with narrow molecular weight subjected to a hydrogenatingreaction in the presence dismbution while controlhg the molecular weight. of a Pd/C catalyst. (1) is produced in high quality and high yield. Allene-Substituted Carboxylic Acid Ester DENKIKAGAKU KOGYO Japanese 4L2002/088,026 Removing Carbon Monoxide A pure allene derivative free from substituent on the MlTSUB1Sr-u HEAVY IND. Japunese AppL 2002/121,008 terminal and with a malonic acid ester (with a 14C CO can be selectively reduced in a Hz-conmining stmight chain alkyl, a branched alkyl with secondaty or gas, to - 10 ppm CO, by passing over a supported Ru tertiary C, allyl, an aromatic hydrocarbon or butadi- metal catalyst at 60-350°C. Gas with an 0Z:CO molar enyl group) is produced using a Pd phosphine catalyst, ratio of 0.01-0.5 is introduced to the catalyst. The and 2-chloro-1,3-butadieneadiene.The diene is reacted with difficulty of 02quality control is avoided. a Na compound of a malonic acid ester.
Plornnm Metals Rm, 2002,46, (4) 193 FUEL CELLS Ruthenium Oxide Film Formation GENERAL ELECTRIC CO U.S. Patent 6,417,062 Platinum-Ruthenium Electrocatalyst RuOz films, for the fabrication of stable thin film NATL. INST. ADV. IND. TECHNOL resistors for microcircuits, are made by forming an J@anese 2002/075,384 AppL inorganic Ru-based (1) on a substrate, and then Manufacture of an electrocatalyst (1) for an elec- hlm thermally decomposing a portion of (1) by exposure trode catalyst joint body in a solid polymer fuel cell to high-intensity radiation, preferably visible light. (SPFC) involves attaching a Pt-Ru catalyst layer to the RuC1,.nHzO and Ru(I1I) nitrosyl nitrate are used as surface of a polymer electrolyte membrane. (1) has the precursors. The method does not require thermal superior oxidation activity for CO and alcohols. The treatment which heats the bulk of the substrate, so SPFC has hgh performance. can be used for non-ceramic substrates in printed circuit boards and flexible circuits. Hydrogen Generating Device MATSUSHITA ELECTRIC IND.]@anese AppL 2002/121,006 Top Spin Valve Sensor HZis efficiently produced in a catalyst-containingHz IBM CORP U.S. Patent 6,437,950 generating device by suppressing catalyst deteriora- A top spin valve sensor includes an IrMn pinning tion due to S. The Hzis produced by contacting a feed layer formed by ion beam sputter deposition. The fuel, such as natural gas or LPG that might contain a magnetoresistive coefficient of the spin valve sensor S-based compound as an odorant, HzO and air, with is increased by placing an IrMnO seed layer between a Pt reforming catalyst. The catalyst also contains a free layer of the spin valve sensor and a first read oxides of La, Ce, Al, Ga, Ti, Mg, Ca, Sr and/or Ba gap layer of the read head. The free layer is preferably with Zr. The HZ can be used in a fuel cell. a NiFe-free film located between the first and second CoFe-free films. ELECTRICAL AND ELECTRONIC Ferroelectric Capacitor with High Ferroelectricity ENGINEERING ROHM CO LTD U.S. Patent 6,437,966 Surface-Metallised Pigmented Optical Body A ferroelectric capacitor, with maintained hgh fer- 3M INNOVATIVE PROPERTIES CO wOd&PL02/41,045 roelectricity, comprises a Si substrate on which is a Si A colour-tailorable, surface-metallised, pigmented oxide layer, a lower electrode of an Ir-Pt alloy, a fer- optical body comprises layered polymeric core(s) con- roelectric layer and an upper electrode. An Ir oxide taining layer(s) of a thermoplastic polymer material. layer is placed on the Si oxide layer, followed by an Ir The thermoplastic polymer layers contain a disper- layer on top, then the ferroelectric layer. The It-Pt sion of a particulate pigment such as C black, Fe alloy of the lower electrode can be formed to corre- oxides, etc. The metallic layer (1) comprises Pt, Ag, spond to the ferroelectric layer. 0 vacancy in the Au, Al, Cu and/or Ni, etc., at the outer surface(s) of ferroelectric layer can be prevented. the polymeric core (2). The transmission spectrum of the optical body differs from those of (1) and (2).The Electrically Conductive Antireflection Film tinted polymeric films are used to provide neutral or NIPPON ELECTRIC GLASS J@anese AppL 2002/071,906 coloured tint, in display devices, mirrors or other An electrically conductive antireflection lilm (1) con- optical equipment. sisting of two layers is claimed. The first layer, of thickness 7&250 nm, contains at least one Pt group Thermoelectric Device metal, Au and/or Ag, and their compounds, and a Co- IBM CORP WodAppL 02/47,178 containing inorganic pigment The second layer has a A thermoelectric device includes an electrical Pt refractive index of 1.3-1.6. (1) is coated on a glass conductor (1) thermally coupled to a cold plate and panel of htgh light transmittance for use in a cathode also a thermoelement electrically coupled to (1). The ray tube. (1) reduces reflected hght, enhances the con- thermoelement has a plurality of Ups to couple it trast, and imparts superior antistatic performance and electrically to (1).The tips provide a low resistive con- electromagnetic wave shielding. nection while minimising thermal conduction between (1) and the thermoelement. The device has improved efficiency and is used for cooling substances, such as MEDICAL USES integrated circuit chips. Microelectrode Catheter for Mapping and Ablation C. R. BARD INC WodAppL 02/47,569 Electroless Ni/Pd/Au Metallisation Structure A catheter (1) for mapping and/or ablation, FUP CHIP TECHNOLOGIES LLC WodAppL 02/58,144 includes a metallic cap of Pt or Au with a plurality of A Ni/Pd/Au metallisation stack is formed upon the apertures and electrode(s) disposed in each aperture. connection pads of integrated circuits at the wafer Electrodes may be paired, or arranged along the level by electroless plating. The interconnection pads length or circumference of the cap. (1)is used to treat can be Cu or Al(1).The lower Ni layer bonds secure- a heart condition by placing it inside the heart and ly to (1) and the intermediate Pd layer serves as an mapping a region of the heart with the mapping elec- out-difhsion barrier for Ni. The upper Au layer can trodes on the catheter or ablation using an ablation receive a variety of interconnect elements. electrode disposed about the mapping electrodes.
Phtinum Metals Rev., 2002, 46, (4) 194 NAME INDEX TO VOLUME 46 Page Page Page Pugc Acres, G. J. K. 64 Blacklock, T. 191 Chiodini, N. 85 Eisenberg, R. I67 Adlhart, C. 87 Blake, A. J. 140 Choi, J.-H. 88 Elangovan, S. P. 189 Aftab, T. 190 Blanco, C. 138 Christensen, P. A. I07 Ellerbrock, J. C. 189 Aizenshtat, Z. 138 Boaretto, R. 85 Ci, Y.-X. 88 Elustondo, F. 140 Akao, T. I90 Bockris, J. O’M. 15 Claridge, J. B. I36 Erickson, J. W. 191 Akgerman, A. I76 Bolton, E. 39 Clark, J. S. I40 Ernst, S. 40 Akporiaye, D. 40 Bonnemann, H. I05 Cliffel, D. E. 14 Ertl, G. 106 Albinati, A. I88 Bontempi, E. 85 Clifford, A. A. 139 Evans, J. 165 Allen, R. J. I90 Borguet, E. I06 Colacot, T. J. 82, Al-Suti, M. K. 189 Borovkov, V. V. 85 180. 190 Anderson, C. 84 Borowski, A. F. 42 Cougnon, C. 94 Fackler, J. P. 176 Angove, D. E. 86 Bos, J. 39 Crabtree, R. H. 2 Factor, B. 39 Antxustegi, M. M. I89 Bossmann, S. 85 Crettaz, R. 87 Falk, L. K. L. 115 Appleton, T. G. 166 Bosteels, D. 27 Cserey,A. 40 Fan,Q.-H. 180 Arata, Y. I88 Boudjouk, P. I38 Cukiernik, F. D. 188 Faria, J. L. 38 Arends, I. W. C. E. 87 Boyall, D. 140 Farmer, V. 191 Armelao, L. 85 Brida, S. I89 Fernandez, J. L. 188 Armor, J. N. 25 Brodil, J. C. 86 Dadgar,A. 42 Feurer,R. 38 Asbton, S. V. 2, 37, 64, Brown, S. D. 38 D’Amico, A. 189 Figoli, N. 40 81. 105, 187 Bruce,D. 137, 165 Danks, T. N. 136 Figueiredo, J. L. 38 Atkinson, I. M. 39 Buchwald, S. L. 87 Darkwa, J. 190 Flores,R. I76 Attard, G. A. 86, I07 Burgos, N. 189 Davies, M. S. 84 Fojta,M. 138 Avdjukhina, V. M. 169 Busch, R. 38 Day, M. W. 38 Ford,M. E. 23 De, G. S. 84 Forster, R. J. 107 Cai, M.-Z. 41 De Clerq, B. 87 Fouletier, J. 191 Baba, A. I. 189 Campagna, S. 85 de Vries, H. 166 Frage,N. 38 Backvall, J. E. I66 Canevali, C. 85 Dehm, C. 42 Freund, H.-J. 24, I90 Baiker, A. 40.41 Cant, N. W. 86, 138 Delmon, B. 138 Friedrich, K. A. I9 I Baltruschat, H. 40 Cao, C. N. I88 Deluga, G. A. 14 Friend, R. H. I89 Bare, S. R. I40 Cardenas T., G. 84 Deng, G.-J. 180 Fu, X. I36 Bartlett, P. N. 106, 168 Carvalho, L. S. 40 Depero, L. E. 85 Fujii, T. I39 Barton, J. K. 165, I66 Castellanos, R. H. 88 Derouane, E. G. 65 Fujishima, A. 84 Bassler, H. I89 Castelli, S. 86 Devillers, M. 138 Fukunaga, A. I89 Bates, F. S. 86 Cawthorn, R. G. I77 Dey, S. K. 39 Funabiki. T. 39 Bazan, G. C. 137 Chan, A. S. C. I80 Dhanya, R. 191 Beckmann, D. I37 Chan, K. S. 188 Di Natale, C. I89 Behm, R. J. 42 Chandler, K. 106 Di Pietro, C. 85 Gaertzen, 0. 87 Bklanger, D. I05 Chang, W.-B. 88 Dickinson, A. J. 191 Gaillard, F. 191 Belokurov, A. P. I36 Chartres, J. D. 39 Diez, F. V. 138 Gam boa-Aldeco, Bennett, S. 24 Chaudret, B. 42 Do Carmo Rangel, M. 15 Bergkvist, K. 1 I5 Chauhan, M. I38 M. 40 Gasteiger, H. A. 42 Bergman, R. G. 166 Che, C.-M. 39 Dolmella, A. I36 Gaudet, J. I05 Bessarabov, D. G. 40 Chen, D.-H. 38 Donnio, B. 188 Geldbach, T. J. 188 Bessard, Y 87 Chen, D.-Y. 88 Douglas, P. 137 Gennero de Chialvo, Bettinali, L. 86 Chen, G. I37 Drent, E. I39 M. R. 188 Beyer, L. 85 Chen, P. 87 Drew, M. G. B. 85 Gent, C. 25 Bkziat, J.-C. I I5 Chen, X. 137 Dudfield, C. 64 Gerhard, A. 189 Billova, S. 138 Chen, X.-M. I80 Diirr, H. 85 Geyer, U. 42 Bimberg, D. 42 Cheng, I. F. I90 Geyzers, K. P. 191 Bischof, C. I89 Chialvo, A. C. I88 Eaton, K. 137 Ghosh, K. 41
Phtinmn Metah h.,2002,46, (4), 195-198 195 Page Page Pugr Pqc.
Giesen, M. 106 Hayes, M. 73 Jaaskelainen, S. 38 Klein Gebbink, Gillies, J. E. 86 Heeger, A. J. I37 James, B. R. 167 R. J. M. 167 Goddard, W. A. 87 Helaja, J. I39 Jang, T. 191 Klemmer, T. J. 140, I9 1 Goldberg, I. I36 Hemhury, G. A. 85 Jenkins, D. J. 86 Knowles, W. S. 82 Goltsov, V. A. 37 Henley, W. H. 136 Jensen, S. F. 40 Kobayashi, A. 39 Golunski, S. E. I68 Henry, C. R. 24 Jiang, J. 85 Kohayashi, H. 39 Gonqalves, J. A. I90 Herber, R. 40 Jiang, R. 191 Kogan, V. I38 Gong, X. I37 Hesek, D. 85 Jirsa, M. 42 Kohler, A. 189 Gonsalvi, L. 87 Hillier, A. C. 50 Jobst, B. 42 Kohno, Y. 39 Gonzalez, F. 138 Hillman, A. R. 107 Johhek, V. I90 Koike, T. I39 GooBen, L. J. 41 Hillmyer, M. A. 86 Johnson, W. L. 38 Kol, M. 136 Gore, E. S. I90 Hirano, M. 136 Johnston, P. 86 Komine, N. 136 Goswami, J. 39 Hiratani, M. 189 Jollie, D. M. 64 Komiya, S. I36 Gottlich, R. I39 Hoffmann, J. 190 Jones, T. 189 Komori, K. 140 Granger, P. 40 Hofmann, P. 87 Jusys, 2. 42 Kondarides, D. I. 24 Grasa, G. A. 41 Hogarth, M. P. 3. Koper, M. T. M. 107 Gratzl, M. 40 117. 146 Kopilov, J. 136 Grigg, R. I90 Holmberg, K. I I5 Kakiuchi, N. 26 Koshevoy, I. 0. 38 Groat, C. G. I80 Honda, K. 84 Kalck, P. 38 Kousmine, R. N. I36 Groth, A. M. 39 Hong, N.-K. I40 Kamer, P. C. J. 41 Kramer, G. J. 26 Grove, D. E. 48, 92, 144 Hong, S.-A. 88 Kamigaito, M. 140 Kua, J. 87 Grushko, B. 38 Honma, Y. 87 Kanai, T. I37 Kuang, Y.-Q. 191 Gu, Y. F. 14 Hope, E. G. I66 Kang, S.-Y. I40 Kuber, A. 190 Guay, D. I05 Horikosi, K. 86 Kani, I. I76 Kucernak, A. 85 Gui, L. I36 Hou, G. I40 Kanki, K. I40 Kuhnert, N. 136 Guillon, D. I88 Howard, J. K. 140, 191 Kanta, A. 88 Kullavanijaya, E. 138 Guo, J. 86 Howarth, 0. W. 190 Kasko, I. 42 Kumaradhas, P. 39 Gusevskaya, E. V. 190 HSU,Y.-N. 140 Katsnelson, A. A. I69 Kuribayashi, K. 88 Gut, D. 136 Hu, J. M. 188 Kawahara, A. I89 Kurokawa, T. 86 Guttmann. M. 85 Hu, R.-H. 41 Kell, D. R. 23 Kwon, B.-K. 88 Hu, S.-W. 88 Kelland. L. R. 165. 166 Kwon. K.-H. 140 Hu, Y. 87 Keller, L. P. I38 Ha, H.-Y. 88 Huang, T.-C. 38 Kempen, A. T. W. 136 Habermiiller, K. 40 Hucul, D. A. 86 Kenna, J. 64 Ladlow, M. 190 Hagihara, T. 39 Hutcheson, R. 190 Keresszegi, C. 40 Lan, X. 88 Hahn, S. F. 86 Khaire, S. S. 86 Lang, H. 84 Hall, M. D. 166 Khan, M. S. 189 Lawson, E. C. 139 Halley, J. W. 106 Kiener, C. A. 87 Layland, R. C. 136 Halligudi, S. B. 86 Iggo, J. A. 167 Kihn, Y. 38 Le Bozec, H. 165 Hamada, N. I90 Ihm, S.-K. 138 Kim, H. 88 Leclercq, G. 40 Hamasaki, S. I40 Ikariyama, Y. 86 Kim, S.4. I40 Leclercq, L. 40 Hambley, T. W. 84 Ikuine, M. 136 Kim, S.-K. I38 Lecomte, J. J. 40 Harada, H. 14 Inabe, T. 39 Kimura, H. I88 Lee, S.-A. 88 Harkins, S. B. 38 Ingelsten, H. H. 115 Kimura, M. I90 Leyarovska, N. I40 Harris, C. A. 86 Inoue, A. 188 Kimura, S. I89 Li, A.-D. 88 Hartmann, J. I90 Inoue, Y. 85, 87 King, D. 24 Li, B. 85 Hartmann, M. I89 Intini, F. P. 136 Kingon, A. I. 42 Li, K. 190 Hashimoto, M. I40 Ishida, A. 188 Kinney, W. A. I39 Li, Q. 38 Haubold, H.-G. I05 Ishihara, T. 189 Kitagaki, M. 39 Li, S. 86 Hauck, B. J. 138 Ito, H. 87 Kitamura, S. 88 Li, X.-H. 39 Haukka, M. 38 Ito, M. 106 Kizek, R. 138 Libuda, J. I90 Havran, L. I38 Itoh, K. I40 Klaui, W. 84 Lima, C. A. S. 84
PkafinnmMetah Rev., 2002,46, (4) 196 Pcrp Page Puh'r Pugc
Limberg, C. 42 Mi, S. 38 Noyori,R. 82, 180 Primet, M. 191 Lin, Z. 167 Miao, W. 85 Nozaki, K. 166 Pugh, R. I. I39 Lindoy, L. F. 39 Michaels, W.C. 40 Puntoriero, F. 85 Ling, H.-Q. 88 Mickelson, G. 140 List, E. J. W. 187 Ming, N.-B. 88 Ocampo, A. L. 88 Liu, D.-S. 180 Miranda, L. C. M. 84 Ohe, K. 41 Qiuhong, H. I15 Liu, R. 140, 190 Misumi, Y. 140 Ohe, T. 41 Liu, X. 85 Mittemeijer, E. J. I36 Ohnishi, T. 139 Liu, Z. 87 Miyaki, M. 189 Oi, S. 87 Ralph, T. R. 3, Liu, Z.-G. 88 Miyano, S. 87 Okamoto, T. 190 117, 146 Loiseau, F. 85 Miyoshi, Y. 39 Oliva, R. 84 Randle, J. 64 Lopez-Castillo, Mizuki, J. 190 Olsbye, U. 40 Rao,T. N. 84 Z. K. 176 Mizumoto, S. 137 Ordbiiez, S. 138 Rath, N. P. 191 Lourdudoss, S. 42 Modica, F. 140 Osakada, K. 139 Rayner, C. M. 139 Lowe, M. P. 39 Moisan, J.-F. 41 Ostrowski, J. C. I37 Reddy, A. K. N. 15 Lu, B. 140 Montes, M. I89 Owen, G. R. I67 Reek, J. N. H. 41 Lubert, K.-H. 85 Morales, J. 190 Reichert, J. 137 Luci, D. K. 139 Morazzoni, F. 85 Reiter, S. 40 Lukehart, C. M. 14 Moreira-Acosta, J. 88 Pacifico, C. 136 Revkevich, G. P. 169 Luo, L. 86 Moreno-Mafias, M. 84 Padovano, G. 136 Reyes, P. 40 Lupton, J. M. 187 Mori, A. 139 Pakkanen, T. A. 38 Rheinwald, G. 84 Mori, M. 139 Palmqvist, A. I I5 Richter, M. M. 39. 137 Moro, M. 87 Park, K.-W. 88 Robertson, J. I40 Ma, H. 88 Moses, D. 137 Parkinson, B. A. 39 Robinson, M. R. I37 Machik, P. 88 Motofusa, S. 41 Patil, S. 187 Rochon, F. D. I88 Maciejewski, M. 24.41 Muegge, B. 39 Patterson, M. J. 86 Rohr, F. 40 Macsari, I. 41 Murakami, M. 42 Paulis, M. 189 Rbnnekleiv, M. 40 Maeda, Y. 26 Muralidhar, M. 42 Paulus, U. A. 42 Roper, W. I65 Majhi, P. 39 Pecchi, G. 40 Ross, J. R. H. 41 Mak, K. W. I88 Pereira, E. C. 137 Ross, P. N. 84 Makino, T. I40 Nabatame, T. 189 Periana, R. A. 87 Rudi, A. 136 Mallat, T. 40 Nair, V. 191 PePina, V. 88 Ruffo, R. 85 Manners, I. 165 Naito, T. 39 Pesquera, C. 138 Ruiz, P. 138 Manor, E. 38 Nakato, Y. 39 Peter, L. M. 15 Ruiz, R. 138 Margesin, B. 189 Nariki, S. 42 Peters, J. C. 38 Rusjan, M. I88 Mari, C. 85 Natile, G. I36 Peters, W. 84 Rytter, E. 40 Markovic, N. M. 84 Nawafune, H. I37 Pettinger, B. 106 Marsh, E. P. I07 Nayar, A. 190 Pieck, C. L. 40 Martynov, M. I. 136 Neckers, D. C. 39 Pinkas, M. 38 Sabo-Etienne, Maryanoff, B. E. 139 Nelson, N. 18 Pinkerton, A. A. 39 S. 42. 167 Masuda, H. 84 Ness, J. S. 86 Pinnow, C. U. 42 Sadler, M. 64 Masuda, T. I40 Neumann, R. 138 Piok, T. 187 Sadler, P. J. 165, 166 Matsuda, H. 39 Nichols, R. J. I07 Platt, C. L. 191 Sakamoto, Y. 84 Matsuda, I. I40 Ning, Y. 108 Pleixats, R. 84 Sandee, A. J. 41 Matsui, Y. 189 Nishiguchi, H. 189 Pogantsch, A. 187 Sarto, F. 86 Mayor, M. 137 Nishihata, Y. 190 Pollack, S. K. 190 Sasamori, K. 188 McCall, M. J. 190 Nishimura, S. 73 Pollington, S. 24 Sastre, H. 138 McClenaghan, N. D. 85 Nishimura, T. 26 Popov, B. N. 88 Sato, M. 188 McLoughlin, S. M. I89 Nishio, K. 84 Porter, L. M. 191 Sauvet, A.-L. 191 Meehan, G. V. 39 Nishioka, T. 137 Poulston, S. 24 Sava, G. 165, 166 Meng, H. M. 188 Nolan, S. P. 41.50 Pregosin, P. S. 167, 188 Sawagucbi, T. I88 Meusinger, J. 25 Noradoun, C. 190 Price, M. A. 86 Sawamoto, M. 140
PhfimmMctuh Rev., 2002, 46, (4) 197 Puge Pogr Prrgr
Scaglione, S. 86 Soudan,P. I05 van Klink, Wilson, J. S. I89 Schauermann, S. 190 Spjelkavik, A. I. 40 G. P. M. I67 Wihiewski, M. 86 Scherf, U. 187 Sridharan, V. I90 van Leeuwen, Wisnoski, D. 139 Scherson, D. A. 107 Stammen, B. I40 P. W. N. M. 41 Wogerbauer, C. 41 Schmid, G. 168 Steigerwalt, E. S. 14 van Oort, B. I39 Wong, P. N. 84 Schmidt, T. J. 42. 84 Stenzel, 0. 42 Venkert, A. 38 Workman, S. 39 Schramm, D. 84 Stimming, U. 191 Verpoort, F. 87 Wright, J. C. 66 Schrobilgen, G. 165 Stitzer, K. E. 136 Viciu, M. S. 41 Wu, D. 88 Schroers, J. 38 Sung, Y.-E. 88 Villarroya, S. 84 Wu, H. 85 Schuhmann, W. 40 Sutton, D. 41 Violante, V. 86 Wu, J. 38 Schulz, R. 105 Svedberg, E. B. 191 Viswanathan, R. I40 wu, L.-z. 39 Schumann, H. 42 Szabb, K. J. 41 Vogel, I. 40 Wu, N. I36 Schuth, F. 25 Volland, M. A. 0. 87 wu, x. 39 Scotti, R. 85 von Hanisch, C. I37 wu, Y. 38 Searles, R. A. 27 Takahashi, S. 165 Sebastian, P. J. 88 Takei, 0. 86 Segre, C. U. 140 Takita, Y. 189 Wakamatsu, S. 140 xu, x. 87 Seibt, M. 42 Tanaka, H. I90 Waldofner, N. 105 xu, Y. 38 Seita, M. 137 Tanaka, T. 39 Walker, A. P. 24 Sengupta, P. S. 84 Tang, Y. I36 Wallnas, M. 42 Serp, P. 38 Tao, K. 85 Wang, C.-C. 38 Yabut, S. C. 139 Serroni, S. 85 Tedesco, A. 191 Wang, C.G. 39 Yae, S. 39 Sethumadhavan, Teles, J. H. 42 Wang, F. 39 Yamabe-Mitarai, D. 191 Terezo, A. J. 137 Wang, J.-X. 87 Y. 74 Shang, Z. 88 Tessier, C. I88 Wang, S. 88 Yamakawa, T. 139 Sharpless, K. B. 82 Thornton-Pett, Wang, Y. I36 Yamamoto, T. 39 Sheela, K. C. 191 M. 190 Waser, J. 87 Yamaura, S. 188 Shekhar, R. 191 Tibuzzi, A. 189 Watson, D. J. 86 Yang, Y. 87 Sheldon, R. A. 87 Tondello, E. 85 Weber, H. B. 137 Yasui, K. 84 Shezad, N. 139 Tong, Y. Y. I07 Wei, B. 87 Yeung, S. K. I88 Shi, J. 140 Tosti, S. 86 Wei, G. I90 Yoon, S.-G. 42 Shieh, WX. 191 Toyama, S. 86 Wei, L.-L. 191 York, A. P. E. 65 Shilov, A. E. 25 Traverso, 0. 85 Weinberg, H. 25 Yoshimura, M. 84 Shin, Y.-W. 39 Trevitt, G. P. 140 Wells, P. B. 86 Yu, T. 88 Shinkai, H. 189 Trimm, D. L. 138 Welton, T. 191 Yue, P. L. I37 Shinmitsu, T. 140 Tryk, D. A. 84 Wenkin, M. I38 Yurechko, M. 38 Shinoda, S. 139 Tung, C.-H. 39 Werner, H. 165 Silva, E. N. 84 Tunik, S. P. 38 White, A. H. 39 Simonet, J. 94 White, K. W. P. 14. 26. Zawadzki, J. 86 Sinha, R. 84 72. IIS, 180 Zen, M. 189 Skelton, B. W. 39 Uemura, S. 26.41 White, P. 14, 17, 105. Zhai, Q. 88 Skoglundh, M. I IS Uenishi, M. 190 107, 116. 176 Zhang, C.-Y. 88 Slavcheva, E. 40 Unwin, P. R. I37 Wieckowski, A. 88 Zhang, J. 137 Smith, D. J. 191 Usami, R. 86 Wierman, Zhang, J. Q. 188 Smotkin, E. S. 140, 190 K. W. 140. 191 Zhang, K. 38 Soderstrom, D. 42 Wild, B. 165 Zhang, L.-P. 39 Sokolov, D. V. 136 Willett, A. 64 Zhang, S.-K. 191 Someya, M. 86 Vad,T. 105 Williams, D. E. 107 Zhang, Y. C. 188 Sommer, F. 136 Vadgama, Williams, J. A. G. 165 Zhao, H. 41 Soncini, G. 189 P. M. 12 Williams, P. 181 Zhao, M.-Z. 88 Song, C.-S. 41 van Dijk, R. 139 Willis, R. R. I90 Zhao, X. 88 Sostero, S. 85 van Ginkel, R. I39 Wilson, C. 140 zur Loye, H.-C. I36
Pkatinnm Metuh Rev., 2000,44, (4) 198 SUBJECT INDEX TO VOLUME 46
Page Page a = abstract Capacitors, (cont.) Acetates, methyl, from MeOH, a I39 memory, Pt-PtO, thin film electrodes, a 88 Acetylenes, phenyl-, oligomerisation, a I90 MlM. Pt thin film electrodes, a I89 polymensation, a 140. 190 Pt/SrBiz zTa20u/Pt.annealing effects, a 88 Acid Chlorides, hydrogenation 73 Carbenes, Pd. N-heterocyclic nucleophilic so Acrylic Acids, asymmetric hydrogenation I80 Ru, a 87. 140 ACTm‘, Pt, Pt-Rh coatings, for the glass industry 181 Carbon Oxides, C02,methanation, a 86 Activation, CHJ. a 87 poisoning, in PEMFC 122 Alcohols, allylic, arylation, a 41 reforming of propane, a 41 C-C bond formation, with enoxysilane, a I40 supercritical, solvent 139, 165, 176 aromatic. transfer dehydrogenation. a 40 CO, chemisorbed, on Pt, PtRu nanoparticles I06 2-arylcyclohexenols, to 2-arylcyclohexenes, a 139 copolymerisation, with ethene, a I39 methyl. conversion. to methyl acetate, a 139 effects in fuel cells 106, 117. 146 decomposition, a 190 electrooxidation 84. 106. 191 electrooxidation I06 poisoning, in PEMFC 118 DMFCs 88, 146 reaction with Oz, a 40 oxidation, a 42, 84 Carbonylation, with aryltin compounds, a 41 oxidation, (I 42,84. 191 Carboxylic Acids, arene-, synthesis, (I 41 aerobic 26 in ketone synthesis, a 41 selective 24 a$-,P.y-unsaturated, hydrogenation 82 Aldehydes, from acid chlorides 73 Catalysis, hook reviews 23, 65. 73 from alcohols 26, 191 conferences 23.24, 165. 167 Alfa Aesar, Fuel Cell Catalysts Brochure 14 heterogeneous, LI 4041.86, 138-139. 189-190 Alkali Metals. iodides. effects on Pd. Pt cathodes. homogeneous, (I 4142,87, 139-140, 19&191 in superdry conditions 94 in ionic liquids, a 191 Alkenes, dihydroxylation 24 low temperature fuel cells 3.64, 117, 146 from alkynes 73 in sc-COz 139, 165, 176 oxidation, a 39 Catalysts, dendrimers 167. 180 Alkoxycarbonylation, chloropyridines, a 87 in fat hardening 23 Alkylacrylates, copolymerisation with ethene, a 139 fixed bed reactors, design aspects 144 Alkynes, hydroalkenylation, a I39 high purity gas production 144 hydroarylation, a 139 homogeneous, supported 23 hydrogenation 73 pgm/C, paste, powder, preferences 48 hydrosilylation. a 138 recycling 24.41. 176, 180. 190, 191 Alloys, dental, a 88 three-way, see Three-Way Catalysts jewellery 66 Catalysts, Iridium, Ir black, NOx reduction 24.41 Aluminium, Al-Mg-Pd, melt oxidation, a 38 Ru02/lrOz, to sustain H20electrolysis, in PEMFCs 132 Al-Pd-Co. U-, V-phase, structures, a 38 Catalysts, Iridium Complexes, [(~od)IrCl]~,a 140 Amination, aryl halides with an ammonia analogue so [Ir(cod)(PPh3)JX, for C< bond formation, a I40 Hartwig-Buchwald so Ir(I), for hetero-Heck type reaction, a 139 Amines, in fast living radical polymerisation. a 140 Catalysts, Osmium, Os,(CO),,Nulcan C. in PEMFCs. a 88 Amino Acids, L-DOPA synthesis 82 Catalysts, Osmium Complexes, Ammonia, oxidation, over Pt 24 OsO, + cinchona alkaloid, dihydroxylation 82, 191 Aquation, cis-, trans-Pt(Ypy),(NO,),, a I88 OsO,/FibreCatTM,dihydroxylation 24 Arenecarboxvlic Acids. svnthesis. a 41 Catalysts, Palladium, KsPPdWI,03..1 2H20/y-AII03./C, Arenes, hydrogenation, h 42. 138 hydrogenation of arenes, a 138 iodo-. homocoupling, u I39 LaFeCoPdO. for automotive emissions control. CI 190 Aroyl Halides, microwave-assisted phenylation, a 87 Lindlar 73 Aryl Halides? arylation, of allylic alcohols, a 41 Pd nanopanicleslAIZOJNiAl, MeOH decomposition, a 190 cross-coupling reactions 50 Pd-Bi/C. glucose selective oxidation, a I38 dehalogenation, a 41 Pd-perovskite. automotive emissions control, (I I90 Heck reactions 50, 139 Pd-Pt/AIMCM-41, n-decane isomerisation, a I89 Suzuki couplings. a 190. 191 Pd/AI,O?, aromatic alcohol dehydrogenation, a 40 Arylation, allylic alcohols. a 41 hydrodechlorination of chlorinated olefins, a 138 a-amino acid esters, (I 87 Pd/A1203+ Mg mesh, phenol hydrogenation, a I90 N-Arylation, aryl indolea 50 Pd/y-Al~O~,4-chloro-2-nitrophenolhydrogenation, a 86 Arylboronic Acids, coupling reactions 41.50 PdAIMCM-41, n-decane isomerisation, a 189 Autocatalysts, technologies adopted by EU 27 PdlBaSO,, hydrogenation of acid chlorides 73 selective poisoning, with thioquinanthrenr 73 Biomimetic Assemblies, in photosynthesis, a 85 Pd/bulk MgO single crystal, particle morphology 24 Book Reviews, “Catalysis of Organic Reactions” 23 PdC. paste, commercial 48.92 Catalysrs Q Cutalysed Reactions 65 liquid phase hatch hydrogenation 92 “Handbook of Heterogeneous Catalytic Hydrogenation powder, commercial 48 for Organic Synthesis” 73 + soluble Bi, glucose selective oxidation, (I 138 “Modern Electrochemistry” 15 Suzuki coupling, a I90 “Progress in Hydrogen Treatment of Materials” 37 Pd/CeOz/AI2O3,thiophene, VOC, oxidation, a I38 Buchwald-Hartwig Couplings 50 PdlFe, Pd/Mg, phenol hydrogenation, a 190 Bushveld Complex, PGE geology, conference I77 PdPb-doped CaCO,, hydrogenation of alkynes 73 modified with pyridine, quinoline 73 Cancer, drugs 88, 165. 166 Pdsupport, aromatic alcohol dehydrogenation, a 40 Capacitors, container, with Pt films, for memory cells 107 PdC12-CuC12.myrcene oxidation, (I 190 MJPLZT/Pt. Pt/PLZT/Pt, H-damage. u 42 transfer of oxide ions, to a catalyst substrate 165
Pkatimm Met& b.,2002,46, (4), 199-204 199 Page Pase Catalysts, Palladium Complexes, n-allyl-Pd, Catalysts, Rhodium Complexes, alknyl-Rh. aryl-Rh. a 87 asymmetric synthesis of (-)-haemanthidine, with fluoroorganic groups. solubility in sc-COr I65 (-)-mesembrane, (-)-mesembrine. in fluorous phases 165 (+)-crinamine, (+)-pretazettine. a I39 Rhz(OAc)r.for 1 ,3-dipolar cycloaddition. (I 191 (q'-aIlyl)Pd intermediate. allylsilanes cyclisation. a 41 Rh-polymer. sc-CO? soluble 176 for cross-coupling reactions SO. 165 [Rh(A)CO]*/SiO2.hydrofortnylation-hydrogenation, a 4 1 (dippf)PdCI>,(dippf)PdCI(CH,), polymerisation. a 190 [Rh-(-)-BINAP(COD)IClO,. in L-menthol process 82 (dppe)PdCI?.(dppe)PdCI(CH>), oligomerisation, LI 190 [Rh(cod)(MeCN):]BF,, conjugate additions, a 87 (dppf)PdC12,(dppf)PdCl(CH,), polymerisation, (I 190 [Rh((R.R)-DiPAMP)COD]BF,. L-DOPA synthesis 82 FibreCatM, Suzuki coupling. a I90 Rh(1). for hetero-Heck type reaction, a I39 N-heterocyclic nucleophilic carbenes. for CX. C-N 50 Rh(1II) salt, carbonylation of aryltin compounds. a 41 Pd, for poly@ara-phenylene) polymer. synthesis 187 [Rh(OH)(cod)],, for internal alkynes + silanediols. a 139 Pd(0) tricyclohexylphosphine. coupling reaction. a 4 1 Rh(TAN,,DPPA)CI, cyclohexene hydrogenation 176 Pd-phosphino-oxazoline allyl, 'meta-dialkyl effect' 1 67 Catalysts, Ruthenium, Pd-polymer-bound phosphine, Suzuki coupling. a 19 1 Pt/Ru, Pt/Ru/Ni. nanoparticles, for DMFC, (I 88 PdClz(Ph3P)>/dpph,alkoxycarhonylation. u 87 PtRu, fuel cell electrocatalysts 14, 88, 106. 117, 146. 191 Pd(dba)? + phosphinobenzene sulfonic acid, a I39 CO tolerance in fuel cells 106, 122 Pd(dba)~/(trimethylphenyl)dihydroimidazolium salt, a 4 1 PtRu/C. fuel cell electrocatalysts 14. 117. 140, 146. 191 Pd>(dba)dphosphine,a-amino acid ester arylation. a 87 Ru-Sn/Y zeolite. MeOH conversion. (I I39 Pd(l1) acetate-pyridine/hydrotalcite,aerobic oxidation 26 methyl acetate formation. (I 139 Pd(I1) salt. carbonylation of aryltin compounds, a 41 Ru/AI?O1,COr reforming of propane. (1 41 Pd(OAc)?,arylation of allylic alcohols. a 41 Rdsepiolite, + Mn, Mo, Zr. for CO? methanation. a 86 Pd(0Ac):. for cross-coupling reactions 50 RuO?, RuOJIrO?, /TiO?, to sustain H1O electrolysis. Pd(OAc)?+ phosphinohenzene sulfonic acid, a I39 in PEMFCs 132 Pd(OAc)?+ PPh,, synthesis of isoxazolidines, (I 190 Catalysts, Ruthenium Complexes, with fluoroorganic Pd(OAc)? + P(o-tolyl),, for coupling reactions, a 139 groups, solubility in sc-CO: 165 Pd(OAch/dppf, alkoxycarbonylation, n 87 in fluorous phases 16.5 Pd(OCOCF1)1/P(2-furyl)l,iodoarene homocoupling. a 139 ["Pr,N][RuO,] + NMO or O?. alcohol oxidation, (I 191 Pd(PPh&C12. microwave promoted phenylation, a 87 permthenate, for CH, activation, a 87 SC. U.S.A., 2000 23 Catalysts, Rhodium, Pt-Rh/AI2O3.TWC. CO + O?,a 40 EuropaCat-V. Limerick, Ireland. 200 I 24 Rh aluminosilicate, laminar, zeolitic structures, a 138 EuropaCat-VI, 2003 24 anchoring [Rh(Me2C0),(2.5-norbornadiene)]C104,a 138 Fuel Cells for Automotive Applications, London. 2002 64 Rh/A1201,film, model catalyst 24 Fuel Cells - Science and Technology 2002. hydrocarbon oxidation. a 86 Amsterdam, 2002 64 + Pt/ALO3. hydrocarbon oxidation. a 86 Thc Dynamic Electrode Surface, Berlin, 2002 I Oh RhRiO?,with propene, NOx reduction 24 Copper,-Pt-Cu, jewellery alloy 66
Pk~tinumMetah Rev., 2002, 46, (4) 200 Page PLI@
Coupling Reactions, (arylboronic + carboxylic) acids, a 41 Electrodes, (mi?.) cross-. for C-C. C-N bonds 50 TiRuO?, anodes, preparation, a I37
homo-, iodoarenes, a I39 Ti/Ru,Mn, ~ ,01anodes. CI2+ O2 evolution, a 188 organosilanes, as coupling agents 50 Electroflotation, of wastewater. n I37 Pd catalysts SO, 165 Electroless Plating, Ag-Pd thin films, for membranes, a 86 see also Heck Reactions and Suzuki Couplings Pt. on SPE membranes, a 40 Creep, in Ir-based refractory superalloys 74 Emission Control, motor vehicles 27, 190 Crystallisation, P&Cu3,,PzoNi,o,a I36 Erbium, Pd-Er-H. H effects on 169 Pd.IINil,Eu?IP211melts, a 38 Etching, Pt, by ICP, using BClKI?,a 140 Cyclisation, allylsilanes, a 41 Ethene, copolymerisation with alkylacrylates. a 139 unsaturated N-chloroamines, to piperidines, a 139 non-alternating copolymerisation with CO, a 139 Cycloadditions, 1.3-dipolar. a 190, 191 Ethers, cyclic enol, by ring-closing enyne metathesis, a 140 Cyclohexenes, 2-aryL. from 2-arylcyclohexenols, N 139 oxidation, a 87 hydrogenation 176 Ethyl Pyruvate, hydrogenation, a 86 Europe, EU adopted emission control, legislation 27 Decomposition, CH,, a 189 Eutectic Reactions, Pd-rare earths 108 MeOH. a I90 NO, (I 86 Films, Co-Pt, sputtered on (001)-oriented Si wafer, a 140 Dehalogenation, aryl halides, a 41 Ir, by MOCVD, a 39 Dehydrogenation, propane, a 40 Pt, by CVD, for memory capacitors 107 transfer, aromatic alcohols, a 40 see also Thin Films Dendrimers, as catalysts 167, 180 'Final Analysis' 2, 48, 92, 144 Os(ll), Ru(l1) polypyridines, photoproperties. a 85 Fracture, in Ir-based refractory superalloys 74 synthesis 165 Fuel Cells, a 42,88, 140, 191 Dental, alloys, a 88 automotive use 24, 64 Deposition, Pd, at C paste electrodes, a 85 catalysts, Pt/C, for MeOH oxidation. a 42 see also Coatings and Electrodeposition for 02reduction reaction. in presence of C1-, a 42 DHPS@,for the glass industry 181 PtRu. CO tolerance 106, 122 Diesel, oxidation catalysts, Pt 27 conferences 24, 64 particulate filters 27 DMFC, anodes 14. 146 selective catalytic reduction 27 cathodes 146 Dihydroxylation, by OsO, 24, 82, I9 I MEAs 146 P-Diketones, Pt(11) with AI(CH1),, for Pt networks 105 miniaturisation 161 Pt(I1) P-diketonates, photoreactions with olefins, a 39 portable applications 161 Dimerisation, of [M(L-L)?(eilatin)]'+, M = 0s. Ru, a 136 electrocatalysts, Pt-RdC, by sulfito method, a 191 2,4-Dinitrotoluene, electron transfer reduction of 94 electrodes. Pt-Ru, nanostructured, CO oxidation. a 191 Ductility, in Ir-based refractory superalloys 74 Fuel Cell Catalysts Brochure. Alfa Aesar 14 HiSPECT" fuel cell catalysts 14, 146 Electrical Conductivity, in (C,H1,NH)[Pd(dmit)2]2,a 39 low temperature, catalysis 3.64, 117. 146 Electrical Contacts, ohmic, Pd/n'-GaAs, a 88 membrane electrode assemblies 3, 117. 140. 146 Pt, with Si interlayers. on p-type Sic, a 191 nanoparticles 3, 88, 117. 146 Electrochemical Cells, CerOxTMwaste process 18 PEFC, Pt-Ru/C electrocatalysts, XANES. a I40 Electrochemistry, a 84-85, 137. 188 MEAs, (I I40 book review 15 PEMFC, air bleed technique 129 cathode reactivity of Pd, Pt, in dry DMF 94 anodes 117 destruction of hazardous organic wastes 18 cathodes 3, 88 doping, of Pt phthalocyanine microcrystals, a 85 CO,, CO. poisoning 117 in fuel cells, see Fuel Cells comparison with DMFC I46 Electrodeposition, 0s. 0salloys, a 189 electrocatalysts, anode, PtMo, PtRu 117 Pt, fine particles. a 39 cathode, Os,(CO),JVulcan C, a 88 see also Coatings and Deposition Pt. Pt alloys 3 Electrodeposition and Surface Coatings, a 39,85, 189 MEAs 3, 117 Electrodes, Au, anchoring of Pt(l1) complex. a 137 water electrolysis. effects 132 Au-Pt black. for glucose sensor, a 86 SOFC, LaSrCrRuO, anode material, a 191 C paste, Pd deposition and dissolution, a 85 see also Catalysts, Iridium, Platinum, Ruthenium conference 106 in fuel cells, see Fuel Cells Gases, high purity HI, Oz 144 Pd. cathode reactivity in dry DMF 94 Geology, book 17 Pt( 11 I). for CO electrochemical oxidation 106 conference I77 Pt, cathode reactivity in dry DMF 94 Glass, production technology 181 for CO electrooxidation 106 Glucose, oxidation 106, 138 in hydrocarbon sensor, a 40 sensors, CI 40, 86 microdisk, in NO sensor, a 40 nanoparticles. + nano-honeycomb diamond films, a 84 Halogenation, of aromatic compounds, olefins, a 42 thin films, for MIM capacitors, a 189 Heck Reactions 50, 139. 165 wire. for in vivo biolo ical sensors 72 High Temperature, Ir-based refractory superalloys 74 Pt-plated Ti, in CerOx"e1ectrochemical cell 18 High Throughput Screening Techniques 24, 87, 190 Pt-PtO, thin films. for memory capacitors, a 88 Hydroalkenylation, alkynes, with silanediols, a I39 PtRu, for CO electrooxidation 106 Hydroarylation, alkynes, with silanediols, a I39 Ru(001). electrooxidation I06 Hydrocarbons, emission control in EU 27 RuOK, in supercapacitors, a 88 oxidation. a 86 n-Si. with fine Pt particles, CI 39 sensor, a 40 Ti2FeRu02,Ti,Fe,Ru,O,,, in supercapacitors I05 Hydrocracking, n-decane, a I89 TiflrOz-TaOs, anode ageing, in HzSOd,a 188 Hydrodechlorination, chlorinated olefins, a 138 Ti/lr0,-Sb~O5-SnO1.wastewater electroflotation, a 137 Hydroformylation-Hydrogenation, 1-octene, a 41
P&nm Metals Rev., 2002,46, (4) 201 Pqr Pqr
Hydrogen, absorption, Pd 37, 169. 188 Luminescence, (cmi.) book review 37 Ru terpyridyls 165 damage of capacitors. a 42 Ru(1I) polypridines. dendrimers. n 85 electrooxidation 117 interaction with Pd. Pd alloys 37, 169 Macrocycles, Pd(ll). Pt(I1). N 39 sensors, a 189 Magnesium, AI-Mg-Pd. melt oxidation, a 38 separation. using Pd-Ag membrane reactor. 189 Magnetism, in CoCrPt perpendicular media, a 191 using Pd-ceramic membranes, a 86 in CoCrPtB layers. on TiZr underlayers. (I 140 solid solutions, in Pd 169 in SrCuRhO, SrNiRhO. a 136 structural changes in Pd, Pd-Er. Pd-W 169 Mass Spectrometry, differential electrochemical, a 42 treatment of materials 37 laser-activated membrane introduction. LAMIMS, a I90 Hydrogenation, acid chlorides 73 Medical Uses, (1 88 a-(acy1amino)acrylic acids, esters 82 PGM Conference 165. 166 alkynes 73 Melting Points, Pt, Pt alloys 66. 181 arenes. a 42. 138 MEAs, in fuel cells 3. 117. 140. 146 asymmetric, acrylic acids 180 Membranes, Pd-Ag, for CHI decomposition. a I89 book review 73 Pd-ceramic, a 86 carboxylic acids, a$-.P.y-unsaturated 82 SPE, with Pt particles. a 40 chiral-catalysed 82 Memory, capacitors for 88. 107 cyclohexene I76 1.-Menthol, commercial synthesis 82 ethyl pyruvate, a 86 Metathesis, of olefins. RCM. ROMP. (I 87 ketones 82, 138 ring-closing enyne. a 140 lignin I67 Methanation, CO.. a 86 in liquid phase batch reactors 48.92 Methane, activation, (I 87 1 -octene I76 decomposition. (I I89 phenols, (1 86. 190 partial oxidation 21 polystyrenes, a 86 steam reforming. a 191 Hydrolysis, cis-,rram-Pt( Ypy),(NOi),, a I88 Microwaves, in phenylation of aroryl chlorides. a 87 Hydrosilylation, alkynes. a 138 in synthesis of [RuCp(dppm)SR].a I36 Hydrotalcites, catalyst suppon 26 MOCVD, Ir films, a 39 Myrcene, oxidation. (I I90 Insulators, single-molecule, tram-Pt(I1) complex. u 137 Ion Source, high temperature, of Pd. a I36 Nanocomposites, Pd:Ag, physical properties, a 84 Ion Transfer, IrCL-. across liquid interface, u I37 Pt-RdGCNF. for DMFC anodes 14 Ionic Liquids, solvents, a 191 RuOK. supercapacitors, a 88 Iridium, films, by MOCVD. a 39 see also Composites Ir( 1 I I), surface, for electrolyte hydration I06 Nanocrystalline Powders, Pd:Ag. a 84 thin films, hy DC sputtering, a 42 Ti,Fe,Ru~O,,.in supercapacitors 105 Iridium Alloys, (Ir. Rh)75Nb15Ni10,specific strength 74 Nanocrystals, Pt-Ru. on GCNF 14 Ir-Nb, Ir-Zr, Ir-Nb-Ni, Ir-Nb-Ni-Al 74 Nanoparticles, Pd, on AI201NAI. model catalyst, a 190 Pt-lr, jewellery alloy 66 embedded in Zr02.H? absorption. a 188 superalloys. refractory: creep. ductility. fracture 74 in HOin-oil microemulsions. n 38 Iridium Complexes, IrClh?-, ion transfer. a 137 stahilised by polyfluorinated chains, (I 84 IIr(DPF)ll. electrophosphorescence, a 137 Pt. 3D networks. Al-organic-stabilised 10s luminescence 137. 165 on y-Al,O,. catalysts I 15 Iridium Compounds, electrodes. (I 137. 188 on C nanospheres. a 38 Ir02, thin films, by DC sputtering, (I 42 with nano diamond films. as electrodes, a 84 IrOJPLZT/Pt, capacitors. a 42 preparation. (I I36 Isomerisation, n-decane, (i 189 in Pt. Pt alloys. fuel cell electrocatalysts 3, 88. 117. 146 Isoxazolidines, synthesis. a I90 Pt. PURL surface diffusion of cheniisorbed CO 106 Nanostructures, PGM Conference I65 Jewellery, Pt, Pr alloys. welding by laser 66 Pt-Ru electrodes. for fuel cells. (I 191 Johnson Matthey, ACTn', Power CoatingsrM 18 1 Nanowires, Pt, u I36 catalysis for fuel cells, research 3. 64. 117, 146 (S)-(+I-Naproxen, synthesis 82 Fi breCat ' '' 24, 190 Nitrogen Oxides, NO, decomposition, (I 86 PGM Conference competition winners 166, 167 sensor. ci 40 "Platinum 2002" 116 NOx, adsorbera 27 Rhodium Bicentenary Competition, winner 2 DeNOx, catalysts 27 reduction 24.41 Ketones, synthesis 26.41. 191 selective catalytic reduction of diesel emissions 27 hydrogenation 82. 138 Nitroxides, reactions with Rh porphyrin alkyls, (I 188 Kumada-Tamao-Corriu Couplings 50 NMR, multi-. aqueous products of Pt(Ypy).(NO,),, a 188 Nobel Prize, Chcmistry, chiral-catalysed reactions. Lasers, to drill cavities in Pt wire electrodes 72 pgm catalysts 82 welding of Pt jewellery 66 Noril'sk, PGE geology. conference I77 Lignin, hydrogenation I67 Liquid Crystals, Rh carboxylate polymers, ci I88 I-Octene, reactions 41, 176 Luminescence, electrochemi-, Ir(ppy),. c/ 137 Ohmic Contacts, see Electrical Contacts Ru(bpy)<'*. a 39, 137 OLEDs, Ilr(DPF)31in PVUPBD. (I I37 Ir terpyridyls 165 Olefins, dihydroxylation. asymmetric. N 191 Os(I1) polypridines. dendrimers. (1 85 as H acceptors. (I 40 photo-. Ir(ppy),, a 137 Kharasch addition, of CCI,. a 87 Pt(I1) quaterpyridine, a 39 metathesis: RCM, ROMP, ci 87 Ru(bpy)<". a 137 with Pt(I1) P-diketonates. photoreactions, (1 39 Pt octaethylporphyrin, CI 137 Oligomerisation, phenylacetylene. (I I90
Phtiinun Metah Rev., 2002,46, (4) 202 Puge Page
Osmium, electrodeposition. a 189 Phase Diagrams, Ag-Pd-Gd-Ru, a 38 Osmium Alloys, electrodeposition, a I89 Ir-Nb-Ni, Ir-Nb-Ni- Al 74 Osmium Complexes, in glucose sensors. a 40 Pd-rare earth systems I08 ground and excited states 106 Phase Transformation Kinetics, Pd-H, Pd-Er-H, luminescence, a 85 Pd-W-H 169 OS~(CO)P.pyrolysis, a 88 Phenols, hydrogenation. N 86, 190 0s.bipy-modified DNA, voltammetric analysis. a 138 wet oxidation, a I38 IOs(L-L),(eilatin)]'+. dimerisation, a I36 Phenylation, aroyl chlorides, a 87 Osmium Compounds, osma-aromatics, osmabenzenes 165 Phosphorescence, from Ir-based OLEDs. a I37 OsO,, in DNA voltammetric analysis, a 138 from Pd-poly@ara-phe@ylene) I87 Os(V111), oxidation state 165 Photocatalysis, in Pt(I1) quaterpyridine complex, a 39 Oxidation, alcohols 24. 26.42, 84. 191 Photoconversion, a 39.85, 137, 189 alkenes. (I 39 PGM Conference 165 chiral-catalysed 82 Photoluminescence, see Luminescence electro-. CO 84, 106, 191 Photoproperties, Pt-phenylene ethynylene formaldehyde. formic acid I06 monomers, polymers. a I89 H: 117 R~(phen)~(3-carbethoxy,4-hydro~y-phen)'+(PF~)~,a 1 89 MeOH 88, 106, 146 Ru polypyridines, biomimetic assemblies, a 85 ethers, a 87 ra~-[Ru(bpy)~(PhP(OMe)~(CI)]Cl.a 85 glucose 106, 138 Ru(I1) bipyridyls. dendrimeric oligomers 165 hydrocarbons, a 86 Photoreactions, Pd(I1) to Pd, by UV irradiation, a I37 liquid organic waste 18 [(PEt,)2HPt(~-Hz)Pt(PEt,)?][BPkll,Pt-Pt homolysis, a 85 melt. Al-Mg-Pd, a 38 [(PEt,),HPt(~-H)hH(PEtl)'][BPh,], Pt-h homolysis, a 85 McOH, a 42.84 [(PEt&PtH,]. [(PEt,),PtH(S)I[BP~],formation, a 85 myrcene, (1 190 Pt(I1) P-diketonates. with olefins. u 39 NH, 24 RmiOz,COz reduction, by HI. a 39 partial. CHI 24 Photosynthesis, Ru polypyridines, as models, a 85 [Pt"CL(Hzenda)]. a 84 Piperidines, from unsaturated N-chloroamines. a 139 thiophene, a 138 "Platinum 2002" I I6 vocs, a 138, 189 Platinum, ACTTM,Power CoatingsTM 181 wet, phenol, a 138 addition to, (NdEuGd)BaCuO, effects, a 42 Oxygen, reaction with CO. u 40 capacitors 42.88, 107. 189 reduction reaction, ORR, for Os,(CO),Nulcan C, a 88 cathodic reactivity, in superdry conditions 94 on Pt/C, for fuel cells. a 42 colloids 105, 136 sensors, a 137 drilling. by laser 72 electrodes, see Electrodes etching, using BCIJCI? gas plasma, a I40 Palladium, AlMgPd ceramic composites, formation. a 38 films 107 cathodic reactivity, in superdry conditions 94 in glass making 181 circuit patterns, on polyimide, a I37 laser welding, iewellery 66 interaction with H2 37, 169 melting point 66. 181 ion source, a I36 nanoparticles 38, 84, 88. 105. 106, 1 IS, 136 nanoparticles, a 38, 84, 188, 190 nanowires. a 136 Pd in poly@arcr-phenylene), phosphorescence 187 ohmic contacts, WSi interlayerslp-type Sic, a 191 PdAg. nanocomposite, a 84 in 0 sensors, a 137 Pd-H. structural changes 169 particles, electroless plated, on SPE membranes. a 40 Pd-rare earth systems. phase diagrams 108 for solar cell electrodes, a 39 Pd/n'-GaAs ohmic contacts, + Ge, Sn layers, a 88 [Pt2-,Na', Nal], reduction of 2.4-dinitrotoluene 94 [Pd,,;, M', MX], [Pd,-, M', ,(MX)I, ekctrogenerdted 94 Pt( I1 I ), surface, for electrolyte hydration 106 solid solutions of H I69 [Pt,,-, M'. MXI, [Pt. , M+,?(MX)!, electrogenerated 94 thin films, a 85, 189 single crystals, for CO electrooxidation, a 84 Palladium Alloys, Ag-Pd-Gd-Ru, a 38 thermal diffusivity 66 Al-Mg-I'd, melt oxidaton, a 38 thin films, a 85, 88, 189 Al-Pd-Co. U-. V-phase, structures, a 38 welding, laser 66 dental, Ag-Au-I'd-Cu, a 88 Platinum Alloys, CoCrPt film, perpendicular media. interaction with HI 37, 169 magnetic properties. a 191 membranes. a 86, 189 CoCrPtB perpendicular media on TiZr, P&I,Cu3UPz,,Nilll,crystallisation, a I36 magnetic properties, a I40 Pd41Ni,,Cu27Pzumelts, crystallisation, a 38 electrodes, see Electrodes and Fuel Cells Pd-Er-H, Pd-W-H, structural changes 169 films, a I40 Pd-Pt, interaction with HI 31 in glass making 181 Pd-rare earths 108 jewellery, Pt alloys 66 Pt-Pd. jewellery alloy 66 laser welding. jewellery 66 Ti(PdNi). shape memory, a 188 melting points 66. 181 Palladium Complexes, (BQA)PdCI, preparation. a 38 nanoparticles 88, 106 (C7H1jNH)I[Pd(dmit),l. air-oxidation of, a 39 Pt-Pd. interaction with Hz 37 (C,HltNH)lPd(dmit),l, electrical conductivity, a 39 Pt-Rh, coatings. ACTrM 181 Pd(l1) N& macrocycles, synthesis, a 39 thermal diffusivities 66 Pd(1I) with pincer-like amido ligand, (I 38 welding. laser 66 in poly@ara-phenylene), synthesis 187 Platinum Complexes, rrans-Pt(II), insulator, a 137 [Pd"CI,J, formation, at C paste electrode, a 85 (BQA)PtCI, preparation. a 38 Palladium Compounds, Pd(NH3)dX. reduction, a 38 (~-C~H1)(Cl)Pt(~-CI),Ru(CI)(11':.rl'-2.7-dimethyl- Na2(Pd2Cln), reduction. a 84 octadienyl), nanocrystal precursor 14 Patents 4347.89-91. 141-143, 192-194 (COD)PtCI, + dimethylphenyl(quinolinyl)amine, a 38 pH, sensors, a 189 luminescence, a 39. 137
Phtinum Metah h.,2002,46, (4) 203 Page PAGE
Platinum Complexes, (cont.) Ruthenium Alloys, (corn.) DhotODrODertieS. (I 189 PI-Ru. jewellery alloy 66 ~hoto;ea~tions.LI 39.85 Ta/Ru bufter layer, for CoCrPt perpendicular media, n 191 precursors for CVD, n 38. 107.189 Ruthenium Complexes, his(~'-2.4-diincthyl- LP~,CI~{N(H)C(BU')O)~],Pt(III)-Pt(llI) distance. (I 136 pentadienyl)Ru(II),for vapour-phase epitaxy, (I 42 lPt24(N(H)C(B~')o),l,o I36 cance; drugs 165, 166 Pt octaethylporphyrin, in 0 sensor, a I37 (~-C2HI)(CI)Pt(~-CI),Ru(Cl)(~':~'-2.7-dimethyl- Pt phthalocyanine, electrochemical doping of, a 85 octadienyl ), nanocrystal precursor 14 [PtIvCl2(enda)l,by oxidation of [Pt"C1dH2enda)], a 84 luminescence 39. 85, 137. 165 [Pt(en)iHzO)z]2',reaction with oL-penicillamine. a 84 (2-MelmH )?[RuC11(2-Mclm ):I. Pt(I1) acetylacetonate, reaction with AI(CHI)J 10s (2-MelniH).[RuC1~(2-Melm)].synthesis. a 84 Pt(I1) N& macrocycles. synthesis. n 39 photoproperties 85, 165, 189 Pt(I1) with pincer-like amido ligand, (I 38 [RuCp(dppin)SR1, micrnwave- ted synthesis, o 136 Pt(II1) 'lantern-shaped'. u 136 [RuH(arene)(Binap)lCF~SO!,piano-stool inverted. (I I88 PtR,(cod), ligand displacement reactions, n 136 [R~(L-L)~(cilatin)]~+,dimerisation. n I36 PtR2L:. H20-soluble diorgano-, synthesis, (I 136 Ruthenium Compounds, electrodes 88. 105, 137. I88 cis-. trcr,is-PtiYpy)2(NOl)l. aquation, hydrolysis, ci 188 LaSrCrRuO. SOFC anode material, (I 191 [Rh,Pt,(CO)lb(dppm)~l,LRhxPt:(C0)21(dppm)?1, n 38 RuO? powders, from RuCIl thermal decomposition, n 137 Platinum Compounds, antitumour agents 88. 165. 166 electrodes, a 88 Selective Catalytic Reduction, + diesel particulate filter 27 K2[Pt(C,0,),], K2PtCIJ.K2PtC16. reduction, n I36 NOx 27 thin films, u 88 Sensors, glucose. (I 40. 86 Platinum Group Elements, geology book 17 H?, CI 189 geology conference I77 hydrocarbons. CI 40 Pollution Control, organic wastes, destruction 18 in viw biological 72 wastewater, electroflotation, (1 I37 NO, (r 40 see also Emission Control 02, (I 137 Polymerisation, co-, a 139 pH, a 189 fast living radical, N I40 Shape Memory Effect, in Ti(PdNi). LI I88 of phenylacetylene. (1 140, 190 Silanes 41. 50, 138, 139. 140 ROMP. a 87 Single Crystals, PI. CO electrooxidation, (I 84 Polymers, coordination, Rh carboxylates, o 188 Sol-Gel, Pt-doped Sn02thin films. a 85 matrix, for Pt complex thin film 0 sensor. (I I37 RuOz. RuO?/Ti anodes, LI I37 polyimide, with Pd circuit patterns, n 137 Solar Cells, with Pt particles on wSi electrodes, a 39 poly(/,aru-phenylene) + Pd. phosphorescence 187 Sonogashira Couplings, of terminal alkynea 50 polystyrenes, hydrogenation. n 86 South Africa, PGE geology, conference I77 Pt-phenylene ethynylenes, photoproperties, (I I89 Sputtering, DC. films. Co-Pt. CI 140 PVKPBD, with [Ir(DPF)&for OLEDs. n I37 thin films, Ir, IrO,. CI 42 Power Coatings'", for the glass industry 181 reactive r.f. magnetron. thin films. PI-PtO,. n 88 Propane, CO, reforming of. CI 41 thin films. Pd-Ag. for Pd-ceramic membranes. (I 86 dehydrogenation, a 40 Stille Couplings, aryl halides + organostannanes 50 Propene, for reduction of NOx 24.41 Sulfuric Acid, Ti/lr02-TaOi anodes, degradation. o I88 Pyridines, chloro-, alkoxycarbonylation, n 87 Superalloys, Ir-based refractory 74 Supercapacitors, RuO-/C, nanoconiposite. (I 88 Rare Earths, Pd-rare earths, eutectic phases 108 Ti2FeRu02.Ti,Fe,Ru-0,,, nanocrystalline I05 solid solublities in Pd. strengthening effects 108 Superconductors, Pt + CeO? additions, a 42 RCM, n 87. I40 Suzuki Couplings, FibreCatT". Pd/C. n I90 Reactors, fixed bed catalyst, design aspects 144 Pd-polymer-bound phosphine. a 191 hydrogen-permeating membrane, a 189 Suzuki-Miyaura Couplings 50 for liquid phase hatch hydrogenations 48,92 Reduction, C02.by HI, CI 39 Tetraalkylammonium Salts, effects on Pd. Pt cathodes. electron transfer. of 2,4-dinitrotoluene 94 in superdry conditions 94 0,. 0 42 Tetralins, amino-, synthesis. n 191 Reforming, (I 41, 191 Thermal Diffusivities, PI, PI alloys 66 Rhodium, Rhodium Bicentenary Competition 2 Thin Films, Ir, IrO:. by DC sputtering. u 42 Rhodium Alloys, (Ir, Rh)7,Nbl,Nii,,.specific strength 74 NilPd, XRD, LI 85 Pr-Rh. coatings. ACT"' 181 Pd, circuit patterns on polyimide. (1 137 jewellery alloy 66 Pd. for poly-Si wires. as H? sensors. n 189 Rhodium Complexes, [ RhoPt(CO)lo(dppm)i]. Pd-Ag. for ceramic composite membranes. n 86 [RhxPt,(CO),I(dppm)21. 38 PI. by chemical vapour deposition, n I89 Rh porphyrin alkyls. reactions with nitroxides, n 188 Pt octaethylporphyrin. for 0 sensors. o I37 tetra(alkoxybenzoato)dirhodium(ll), liquid crystals, a I88 Pt-doped SnO?. sol-gel preparation. (I 85 pyrazine adducts, liquid crystals, a 188 Pt-PtO,. for memory capacitor electrodes. a 88 TpmsRh(LL) (LL = (CO)?,cod, nbd). Rh(I) chemistry, CI 84 Ti(PdNi), bhape memory hehaviour. ti 188 Rhodium Compounds, SrCuRhOh, Sr,NiRhOh, LI 136 see also Films ROMP, n 87 Thinpenes, oxidation, n I38 Rosenmund Reduction, acid chlorides 73 Three-Way Catalysts 27.40 effect of HIO 48 Tungsten, Pd-W-H. H effects on I69 Russia, PGE geology. conference 177 Pt-W. jewellery alloy 66 Ruthenium, electrodes I06 Ru-doped InP. resistivities. a 42 VOCs, oxidation. (I 138, 189 Ru(001), surface, for electrolyte hydration 106 Voltammetry, (DNA-0s.bipy ). microanalysis. n 138 Ruthenium Alloys, Ag-Pd-Gd-Ru, a 38 electrodes, see Electrodes and Fuel Cells Water, waste, electrode system for electrollotation. u 137 nanoparticles 88. 106 Welding, laser. of PI jewellery 66
Pkztin#m Metalj Rm, 2002,46, (4) 204