WO 2013/138845 Al 26 September 2013 (26.09.2013) P O P C T

(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization I International Bureau (10) International Publication Number (43) International Publication Date WO 2013/138845 Al 26 September 2013 (26.09.2013) P O P C T

(51) International Patent Classification: (81) Designated States (unless otherwise indicated, for every C25B 1/02 (2006.01) C01B 3/00 (2006.01) kind of national protection available): AE, AG, AL, AM, C25B 1/30 (2006.01) C01B 15/01 (2006.01) AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, C25B 11/06 (2006.01) BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, (21) International Application Number: HN, HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KN, KP, PCT/AU20 13/000232 KR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, (22) International Filing Date: ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, 12 March 2013 (12.03.2013) NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, (25) Filing Language: English TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, (26) Publication Language: English ZM, ZW. (30) Priority Data: (84) Designated States (unless otherwise indicated, for every 2012901 138 22 March 2012 (22.03.2012) AU kind of regional protection available): ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ, (71) Applicant: MONASH UNIVERSITY [AU/AU]; Welling UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, ton Road, Clayton, Victoria 3800 (AU). TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, (72) Inventors: MACFARLANE, Douglas; 9 Camperdown MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, Street, Brighton East, Victoria 3187 (AU). IZGORODIN, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, Alexey; 9/1 18 Waverley Road, East Malvern, Victoria ML, MR, NE, SN, TD, TG). 3145 (AU). Published: (74) Agent: SMOORENBURG PATENT & TRADE MARK ATTORNEYS; PO Box 515, Ringwood, Victoria 3134 — with international search report (Art. 21(3)) (AU).

(54) Title: PROCESS AND CATALYST-ELECTROLYTE COMBINATION FOR ELECTROLYSIS (57) Abstract: The invention relates to a process for electrolysis comprising a cathode and an anode comprising a catalyst, both the cathode and anode at least partly immersed in an electrolyte, the process characterised in that the electrolyte at least partly inhibits further oxidation of a product formed at the anode. Typically the catalyst comprises one or more metal-(Group Vlb) semiconductors, and one or more metal-(GroupVlb))- phosphorous species. PROCESS AND CATALYST-ELECTROLYTE COMBINATION FOR ELECTROLYSIS

FIELD OF INVENTION

[0001] The present invention relates to the field of electrolysis, particularly water electrolysis including water oxidation or water splitting,

[0002] In one form, the invention relates to a process and apparatus for electrolysis.

[0003] In one form, the invention relates to a new catalyst-electrolyte combination for electrolysis.

[0004] In one particularly preferred aspect the present invention is suitable for electrolytic generation of hydrogen peroxide or radicals capable of forming hydrogen peroxide.

[0005] It will be convenient to hereinafter describe the invention in relation to processes for generating hydrogen peroxide, or radicals capable of forming hydrogen peroxide and hydrogen, however it should be appreciated that the present invention is not limited to that use and can be applied to other processes and generation of other products.

BACKGROUND ART

[0006] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor's knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein. Hydrogen Peroxide

[0007] Hydrogen peroxide (H20 2) is a strong oxidising agent and is considered a highly reactive oxygen species.

[0008] Its oxidising capacity is so strong that in concentrated form it is used as a rocket propellant. Its strong oxidising capacity makes it particularly well suited for use as a bleach, cleaning agent and antimicrobial for industrial and domestic use. One of the advantages of hydrogen peroxide is that it is a stronger oxidising agent yet more environmentally acceptable than chlorine based oxidising agents.

[0009] The market for hydrogen peroxide is large and continues to expand, for example, from about 1.9 million tonnes in 1994, to 2.2 million tonnes in 2006, to an estimated 4.3 million tonnes 2012. Due to the potential hazardous nature of the processes that involve production, storage and transportation of hydrogen peroxide at high concentration, significant interest recently has been given to the development of alternative production methods, particularly in-situ processes.

[0010] Hydrogen peroxide is principally manufactured by the 'anthraquinone process' consisting of the autoxidation of a 2-alkyl anthrahydroquinone (or 2-alkyl-9,10- dihydroxyanthracene) to the corresponding 2-alkyl anthraquinone. For example, the cyclic reaction depicted at equation (1) shows the oxidation of 2-ethyl-9,10- (C dihydroxyanthracene 16 H12(OH)2) to the corresponding 2-ethylanthraquinone

(Ci 6H 20 2) and hydrogen peroxide. [001 1] Most manufacturers use the Riedl-Pfleiderer process, which includes the step of bubbling compressed air through a solution of the anthracene. Oxygen in the air reacts with the labile hydrogen atoms of the hydroxy group, giving hydrogen peroxide and regenerating the anthraquinone. The hydrogen peroxide thus generated is extracted and the anthraquinone derivative is reduced back to the dihydroxy (anthracene) compound using hydrogen gas in the presence of a metal catalyst. The cycle is then repeated.

[00 ] The overall equation for the process is:

→ H2 + 0 2 H20 2 equation (2)

[0013] The economics of the process depend heavily on effective recycling of the quinone (which is expensive), extraction solvents, and the catalyst and many attempts have been made to improve the economics of the process.

[0014] For example Solvay have improved productivity and reduced the cost of production by optimising the distribution of isomers of 2-amyl anthraquinone and pursuing economies of scale. This improved process was implemented in 2008 in a "mega-scale" single-train plant in Zandvliet (Belgium) and another in 20 1 in Map Ta Phut (Thailand). (Hydrogen Peroxide 07/08-03 Report, ChemSystems, May 2009).

[0015] Processes for producing hydrogen peroxide directly from the elements has been of interest for many years. However, one of the problems associated with this approach is that the reaction of hydrogen with oxygen thermodynamically favours production of water. · While use of a finely dispersed catalyst is beneficial for promoting selectivity to hydrogen peroxide, the selectivity is still not sufficiently high for commercial development of the process. In an effort to improve the selectivity researchers have developed minute (nanometer-size) phase-controlled noble metal crystal particles on carbon support. Evonik Industries, established a pilot plant in Germany in late 2005 using this catalyst and has claimed that there are reductions in investment cost because the process is simpler and involves less equipment. However, the process has the drawbacks of being more corrosive and unproven and yields low concentrations of hydrogen peroxide (about 5-10 wt% as compared with about 40 wt% via the anthraquinone process).

[0016] In 2009, another attempt was made to develop a process for direct synthesis using a gold-palladium nanoparticulate catalyst. (G.J. Hutchings et al, Science 2009, 323, 1037) The catalyst is claimed to have the advantage of reducing hydrogen peroxide decomposition and potentially being an inexpensive, efficient and environmentally friendly process. Hydrogen peroxide tends to decompose spontaneously, and even more rapidly under the influence of the catalysts typically used in direct synthesis. However the use of a gold-palladium nanoparticulate catalyst typically achieves only very low concentrations of hydrogen peroxide (less than about 1-2 wt%).

[0017] Attempts have also been made to produce alkaline hydrogen peroxide using a monopolar cell to electrolytically reduce oxygen in a dilute sodium hydroxide solution. (Hydrogen Peroxide 07/08-03 Report, ChemSystems, May 2009).

" (Anode) 20H - H20 + 1/20 2 + 2e equation 3(i)

~ (Cathode) H20 + 0 2 + 2e - H0 2 + OH equation 3(ii)

(Overall) NaOH + 1/20 2 -» H0 2Na equation 3(iii)

[00 8] It was shown recently that significantly lower production costs can be achieved in the system where hydrogen and hydrogen peroxide are produced simultaneously by water electrolysis. (Ando, Y. and Tanaka T., 'Proposal for a new system for simultaneous production of hydrogen and hydrogen peroxide by water electrolysis', International Journal of Hydrogen Energy, 2004, 29(13), 1349-1354).

+ → 20 2 + 2H + 2e H20 (E0 = 0.69 V vs NHE) equation 4(a)

→ + 2H20 HOOH + 2H + 2e (E0 - .776 V vs NHE) equation 4(b)

→ + 2H20 0 2 + 4H + 4e (E = .23 V vs NHE) equation 4(c) + 4H + 4e 2H2 (E0 = 0 V vs HE) equation 4(d)

[0019] In order for this system to be viable, however, the water oxidation catalyst should promote formation of hydrogen peroxide and inhibit the oxygen evolution reaction (equation 4(c)) which is the more thermodynamically favourable process.

[0020] A number of carbon electrodes allowed simultaneous production of hydrogen and hydrogen peroxide using 2V total cell potential. However the efficiencies of this process for hydrogen peroxide production (30-50%) and low current densities are not sufficient for practical use. It is clear that the development of catalyst/electrolyte combination which allows water splitting according to equations 4(b) and 4(d) with high efficiency and low overpotential would allow significant reduction in the energy cost of production for hydrogen and hydrogen peroxide via electrochemical water spitting. Alternatively high efficiency electrolysis according to 4(a) and 4(b) would allow hydrogen peroxide production at both electrodes.

[0021] The ability to split water to produce hydrogen simultaneously with hydrogen peroxide is of interest in the field of alternative energy technologies, particularly the use of hydrogen production as the main energy carrier in the proposed "hydrogen economy". The fundamental processes for producing and converting hydrogen are well-known and the technologies have proven to be practical in large-scale operation. However, current low temperature water electrolysis processes are only 50-62% energy efficient and a cost analysis as part of the United States Council for Automotive Research, Department of Energy (USCAR/DOE) Hydrogen Roadmap suggests that efficiency improvements to 74% are needed in order to meet the DOE cost goal for hydrogen of $2-$3 per 'gallon of gas equivalent'. The biggest source of inefficiency in these water electrolysis cells is the oxygen generating electrode where substantial over-potentials, typically in excess of 450 V, are required to generate useful rates of water oxidation. For this reason there has been a major research effort devoted to the development and understanding of novel water oxidation catalysts.

[0022] Ideally a water oxidation catalyst should be based on abundant, low cost materials, have high turnover frequencies and remain active over prolonged periods of time. Currently, commercial electrolysers are based on nickel anodes, which require high operational overpotential, and hot alkaline solutions. The most efficient catalysts known are those based on transition metal oxides including, MnO , C03O4, RUO2, an Ir02. On the other hand it has recently been suggested that a process for water electrolysis that proceeds via hydrogen peroxide rather than oxygen may be more energy efficient. In smaller scale processes the hydrogen peroxide itself may be of significant value. In large scale fuel process, the hydrogen peroxide could be directly disproportionated into oxygen and water.

[0023] Accordingly there is an ongoing need for processes having improved efficiency or economy for production of hydrogen peroxide.

[0024] There is also a need for processes that have reduced reliance on consuming energy from non-renewable sources such as fossil fuels.

SUMMARY OF INVENTION

Λ [0025] An object of the present invention is to provide a process for electrolysis having improved efficiency or yield or lower environmental impact compared to analogous processes of the prior art.

[0026] Another object of the present invention is to provide a catalyst-electrolyte combination for electrolysis.

[0027] Another object of the present invention is to provide an electrochemical process for production of hydrogen peroxide, or radicals capable of forming hydrogen peroxide or hydrogen that can consume energy from a renewable source.

[0028] A further object of the present invention is to alleviate at least one disadvantage associated with the related art.

[0029] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems. [0030] In a first aspect of embodiments described herein there is provided a process for electrolysis comprising a cathode and an anode comprising a catalyst, both the cathode and anode at least partly immersed in an electrolyte, the process characterised in that the electrolyte at least partly inhibits further oxidation of a product formed at the anode.

[0031] Typically the electrolyte inhibits further oxidation by solvating the product formed at the anode.

[0032] In a second aspect of embodiments described herein there is provided a process for electrolytic generation of hydrogen peroxide or radicals for hydrogen peroxide formation, the process comprising the step of passing a current between a cathode and an anode comprising a catalyst, both the cathode and anode being at least partly immersed in an electrolyte comprising a strongly proton-accepting species.

[0033] In a particularly preferred embodiment the electrolyte comprises a solvent and one or more dissolved species comprising a strongly proton accepting species. The electrolyte could, for example comprise a basic nitrogen or phosphorus group, and may be substituted. Suitable proton accepting species include (alkyl substituted) pyrrolidine or (alkyl substituted) imidazole. Primary, secondary or tertiary substituted amine groups may be suitable - the tertiary substituted species being less preferred due to their tendency to be easily oxidised. The amine groups would typically be substituted with H, alkyl, aryl, Ph or Bz groups. The electrolyte could comprise an anionic nitrogen or phosphorous species, such as dicyanamide ((CN^N ").

[0034] The electrolyte may also include an ionic component to ensure that the conductivity of the solution is adequate for electrochemical processes. The ionic component can be a simple salt that is otherwise inert in the process. Alternatively the ionic component can be the protonated form of the proton accepting species. For example if an amine is used in this role, partial neutralisation of the amine with for example sulphuric acid will produce ammonium ions and bisulphate and sulphate ions to fulfil the role of the ionic component. This approach allows facile adjustment of the pH of the electrolyte. It is important in this approach, however, that the neutralisation be only partial so that some level of amine content remains. [0035] The solvent component of the electrolyte may be any suitable liquid such as water.

[0036] The solvent component may also be any other solvent which is electrochemically stable at the electrochemical potentials required, for example acetonitrile or glutaronitrile. The solvent component may also be an ionic liquid. In these cases water is added as needed as a reactant to the electrolyte.

[0037] In a preferred embodiment the electrolyte is butyl ammonium sulphate dissolved in water.

[0038] In particularly preferred embodiment the catalyst comprises:

• one or more metal-(Group VIb) semiconductors, and

• one or more metal-(GroupVlb))-phosphorous species.

[0039] For example the metal-(Group VIb) semiconductor may correspond generally to the formula MmA a wherein:

• M is a metal,

• A is a Group VIb species, and

• m and a have a value of between 1 and 5 .

[0040] Furthermore, the metal-(Group Vlb)-phosphorous species corresponds generally to the formula M' A'a'Py wherein:

• M' is a metal and may be the same as M,

• A' is a Group VIb species and may be the same as A ,

• m, m', a and a' have a value of between 1 and 5 , • P is a phosphorous species, and

• y has a value 0< y <5.

[0041] The metal ( or M') may be any metal traditionally used in semiconductors, but would typically include elements such as Ti, Mo, n, Fe, Co, Ni, Cu, n, Ga, r, Cd, In, Sn and the rare-earth metals. The term 'metal' is to be construed as including one elemental metal or combinations of two or more elemental metals.

[0042] The Group Vlb species (A or A') may include any non-radioactive member of the chalcogens, namely oxygen, sulphur, selenium and tellurium. For the avoidance of doubt, references herein to Group Vlb is designated according to the old lUPAC (European) system and corresponds to (i) Group VIA of the CAS (American) system, and (ii) Group 16 of the new lUPAC system. (Leigh, GJ, Nomenclature of Inorganic Chemistry: Recommendations 1990, Blackwell Science.)

[0043] In a particularly preferred embodiment the process is used for generation of hydrogen peroxide or radicals capable of forming hydrogen peroxide. Said radicals are typically extremely short lived and highly reactive, having oxidation states intermediate between H20 and H20 and includes solvated species.

[0044] The hydrogen peroxide thus produced may be consumed for a range of commercial or industrial products. It may be used in-situ in the electrolyte to carry out oxidation reactions of substrates of commercial or industrial importance in which hydrogen peroxide is typically used. Such a process could be carried in a continuous or semi-continuous fashion if the substrate is added and the oxidised products removed continuously from the electrolyte. Alternatively the hydrogen peroxide or radicals capable of forming hydrogen peroxide may be formed as an intermediate, for example in the water splitting process for the production of hydrogen.

[0045] Without wishing to be bound by theory, it is believed that in the process of the present invention, the H20 2 dissolves into the electrolyte, stabilised by interactions with the electrolyte species. These interactions may take the form of hydrogen bonding interactions. Complex formation may also take place depending on the nature of the electrolyte. The catalyst electrolyte combination diverts the water oxidation process into hydrogen peroxide production according to equation 5;

+ 2H20 H20 2 + 2H + 2e equation (5)

[0046] Optimally, the process is additionally used for water electrolysis to produce hydrogen and has the advantage that no gaseous oxygen is directly produced. By contrast, oxidation processes of the prior art directly oxidise water to oxygen which requires large over-potentials (energy losses), the oxygen additionally being detrimental to cell components, the efficiency of the hydrogen producing reaction and the purity of hydrogen stream.

[0047] In yet a further aspect of embodiments described herein there is provided a process for generation of hydrogen peroxide by electrolysis comprising the step of passing a current between a cathode and a MnO coated gold anode, both the cathode and anode being at least partly immersed in an electrolyte comprising butylammonium sulphate.

[0048] In further aspect of embodiments described herein there is provided an electrolytic cell for generation of hydrogen peroxide by electrolysis, the cell comprising a

cathode and a MnOx coated gold anode and an electrolyte comprising butylammonium sulphate wherein in use both the cathode and anode are at least partly immersed in the electrolyte during the passing a current between the cathode and anode.

[0049] Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.

[0050] In essence, embodiments of the present invention stem from the realization that a catalyst electrolyte combination could be used to inhibit oxidation of a product formed during electrolysis. With particular reference to hydrogen peroxide production, it has been realised that this can be used to divert a water oxidation process into hydrogen peroxide production by solvating the hydrogen peroxide and moving it away from the electrode so that further oxidation does not readily take place. Put differently, it is clear that the development of catalyst/electrolyte, combination which allows water splitting according to equations 4(b) and 4(d) with high efficiency and low overpotential would allow significant reduction in the energy cost of production for hydrogen and hydrogen peroxide via electrochemical water splitting. Alternatively high efficiency electrolysis according to 4(a) and 4(b) would allow hydrogen peroxide production at both electrodes.

[0051] Advantages provided by the present invention comprise the following:

• it permits the generation of hydrogen peroxide by electrolysis, that is, by use of electricity as the energy source as compared prior art processes which typically use fossil fuels as the energy source;

• it provides an alternate oxidation process for water that does not directly product gaseous oxygen, thus avoiding oxidation detrimental to cell components and hydrogen stream;

• it supports high efficiency, low overpotential oxidation of water to hydrogen peroxide.

[0052] Other advantages of the present invention can be illustrated by reference to the following two non-limiting applications of the present invention:

(i) Hydrogen peroxide production for use in-situ or use, after separation from the electrolyte, in all of the standard applications of hydrogen peroxide:

[0053] In-situ use would involve contacting the hydrogen peroxide solution in the electrolyte with a substrate that is to be oxidised. Extraction of the oxidised substrate affords the product. For example, the oxidation process which is the subject of this invention can be coupled in a reactor in which wood pulp bleaching is carried out, the continuous production of hydrogen peroxide rendering this process more efficient.

[0054] Optimally for this application the water oxidation process would be coupled with an oxygen reduction electrode which produces hydrogen peroxide at the cathode through the reduction of oxygen gas according to equation 6 . 202 + 4e- + 2H20 → 2HOO- + 20H- ... .equation 6

[0055] Thus hydrogen peroxide is simultaneously produced at both electrodes. This process allows generation of the hydrogen peroxide on-site at chemical installations where it can be consumed, avoiding transportation costs.

[0056] For off site use, extraction can also be used to recover the standard hydrogen peroxide solution that is used widely in the chemical industry.

(ii) Use in water splitting processes

[0057] Water splitting processes under development in laboratories around the world rely on water oxidation as the overall oxidation process. This typically requires large over-potentials and therefore large energy losses. The catalyst/electrolyte combination of the present invention provides a more efficient water oxidation process. By restricting the oxidation to hydrogen peroxide production lower over-potentials can be utilised, improving the overall energy profile of the process. The hydrogen peroxide solution created can then be caused to decompose by a second catalyst via equation 7:

H 0 + O equation 7 2H20 2 « 2

[0058] This second step can be carried out in situ in the water electrolysis cell. Alternatively, in a preferred embodiment, the electrolyte can be drained into a separate cell containing a bed of the second catalyst to thus initiate release of the oxygen. This provides the advantage of removing oxygen bubbles from the vicinity of the water oxidation electrode where the oxygen bubbles would otherwise have a damaging corrosive effect.

[0059] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which:

• Figure 1 illustrates linear scan voltamograms of the MnOx electrodes in BAS electrolyte and aqueous NaOH electrolyte performed at scan rate of 1 V s ;

• Figure 2 illustrates absorbance of MnO at 565 n added to the BAS electrolyte after (a) electrolysis (200mC) to form hydrogen peroxide and (b) after addition of a known amount of standard hydrogen peroxide;

• Figure 3 illustrates the concentration of H20 2 detected over time in the BAS

electrolyte with and without Mn0 2 disproportionation catalyst; and

• Figure 4 illustrates diphenylamine redox indicator in as prepared BAS electrolyte, BAS with electro chemically produced hydrogen peroxide and BAS with standard hydrogen peroxide.

DETAILED DESCRIPTION

[0061] Aspects of the invention will be further described with reference to the following non-limiting examples:

[0062] Materials: Manganese (II) acetate tetrahydrate 99.99% (Mn(Ac)2-3H20), butylamine 99.5%, ethylamine 99.5 % and sulphuric acid were purchased from Sigma- Aldrich Pty. Ltd. Nitric acid was purchased from Merck. Potassium permanganate, oxalic acid, diphenylamine. Hydrogen peroxide. Unless otherwise stated, reagent grade water (18 ΜΩ-cm resistivity) was used for all experiments. All chemicals were used as received. [0063] Ethyl ammonium nitrate (EAN) was prepared by mixing ethylammonium hydroxide with nitric acid. A typical procedure for EAN synthesis is as follows: 50 ml of ethylamine (0.76 mole) was added to 200 ml of water and kept agitated using magnetic stirring. Then a small amount 2 nitric acid solution was added drop wise until pH 7 was recorded using a Mettler Toledo InLab® micro pH electrode. Finally water was removed from the mixture over 2 hours in a rotary evaporator at 50°C and 20 kPa.

[0064] The electrolyte for hydrogen peroxide synthesis - butyl ammonium sulphate (BAS) was prepared by mixing 0.08 moles of butyl amine with 0.04 moles of sulphuric acid in a 100ml standard volumetric flask. High ionic strength butyl ammonium sulphate electrolyte (BAS-IL) was prepared by mixing 0.4 moles of butyl amine with 0.2 moles of sulphuric acid in a 100ml standard volumetric; this yields salt water mixture. The pH of the electrolytes was adjusted to 0 through addition of small amount of butylamine with pH recorded using a Mettler Toledo InLab® micro pH electrode.

[0065] Electrochemical experiments: Electrochemical experiments were performed on a PAR VMP2Z potentiostat with a standard three-electrode configuration. The MnO films deposited on Au electrodes were used as an anode with a Pt counter electrode used as cathode. The working area of the electrode was masked using Kapton tape, leaving a 0.5 cm x 0.5 cm electrode area. A 66-EE009 ("No-Leak") Ag/AgCI (Cypress Systems) and standard calomel electrodes were used as a reference. All electrochemical measurements unless otherwise stated were performed at room temperature (RT) of about 22°C.

[0066] MnOx Electrodeposition: Thin films of MnOx were deposited on the gold electrodes from ethylammonium nitrate ionic liquid with 10 vol. % of water and 0.01 M manganese acetate at 120°C using constant current density of 200 µΑ cm 2 for 10 minutes, as described in more detail elsewhere.

[0067] Characterisation techniques: The amount of hydrogen peroxide was determined using a solution of potassium permanganate. A stock solution of 0.1 9 M potassium permanganate was prepared and standardised. A diluted solution of 5.78-1 0'3 M potassium permanganate was used for titration. In a typical procedure 0.25 ml of 0.8 BAS electrolyte at pH 10 was added to the 0.25 ml of 1M H2S0 and titrated using 5.78 10 3 M potassium permanganate solution.

[0068] A useful second indicator for the presence of hydrogen peroxide involves its action as an oxidant, reflecting its possible use for in-situ oxidation reactions. Thus 1% of diphenylamine in concentrated sulphuric acid was oxidised in the H2O2 solution. In a typical procedure 0.1 ml of 0.8 M BAS electrolyte at pH 10 was added to the 0.2 ml of the diphenylamine solution.

[0069] UV-Vis transmission spectra were recorded at room temperature using a Cary 1E UV-visible spectrophotometer.

[0070] Results: Linear scan voltammograms of the manganese catalyst were measured in a range of electrolytes and are shown in Figure 1. High oxidation current densities were observed in BAS and BAS-IL electrolytes at oxidation potential above 0.5 V vs. SCE. It can be seen, however, that there were only negligible current densities at potentials below 0.6 V vs. SCE when aqueous sodium hydroxide was used as an electrolyte. Similarly low currents were observed in the neutral BAS electrolyte, in accord with the previously reported low catalytic activity of manganese based catalysts in neutral electrolytes.

[0071] The equilibrium potential for water oxidation at various pH's can be calculated from E a o i = 1.23 - 0.059 (pH) - 0.244, V vs. SCE. It can be seen that at pH 10, the equilibrium potential for water oxidation is around 0.4 V vs. SCE and high overpotential is required to oxidise water in the electrolyte containing sodium hydroxide. The neutral BAS electrolyte shows very little activity, indicating that this currents involved at pH 10 are the result of a strongly pH sensitive process.

[0072] Attempts to determine oxygen production from the electrolysis at pH 10 produced only very small rates of oxygen evolution. Oxidation of the electrolyte was also investigated as oxidation of amines is a well known process, though typically at higher potentials than those in use here. Despite passage of substantial quantities of charge no evidence of ' decomposition was seen in Nuclear Magnetic Resonance or mass spectroscopy (ESI) results. This led us to suspect the formation of some product of water oxidation intermediate between water and oxygen. Classic colourmetric tests for hydrogen peroxide including potassium permanganate reduction and diphenylamine

oxidation both proved strongly positive for the presence of H20 2.

* [0073] In order to determine efficiency of the process for hydrogen peroxide production a series of electrolytes was used during oxidation at constant potential of 0.59 V vs. Ag/AgCI. The amount of charge passed was kept at 200mC and equivalent to .04 pmoles of H2O2 based on Faraday's law assuming a 2 electron oxidation of water. Standard titration of hydrogen peroxide with potassium permanganate solution assumes reduction to n(ll) as per equation 7 .

4 + → 2+ 2Mn0 + 5H20 2 + 6H 2Mn + 50 2 + 8H20 equation 7

[0074] In order to improve sensitivity, electrolytes were titrated in a standard UV-Vis cell, with the amount of potassium permanganate determined by measuring absorbance value at 565 nm. The value of absorbance at 565 nm as a function of amount of potassium permanganate added to a pH 10 BAS electrolyte after 200mC oxidation is shown in Figure 2a. The end of titration was determined as a point where a linear fit function of the absorbance at high amount of titrant added extrapolates to zero. In the example of Figure 1 the end point is taken as 55.4 L, which is equivalent to 0.08 oles

of H20 2 or a production yield of about 77% from Faraday's Law for a 2 electron process.

In a control experiment where 1.04 pmoles H20 2 was directly added to the electrolyte medium, as can be seen in Figure 2b, the detected amount of H2O2 was around 86%.

[0075] The hydrated ionic liquid form of this electrolyte (BAS-IL) produces the highest currents at any given overpotential (Figure 1). To the extent that the formation of a solvated hydrogen peroxide species involving the electrolyte is the rate determining step in this process, it is to be expected that the high salt concentration will enhance the rates of reaction. Lower production yields of about 64% were obtained from the titration of the BAS-IL electrolyte after 200mC of electrolysis.

[0076] The lower than 100% efficiency detected in these experiments may be due to the competing process of water oxidation to oxygen during the electrolysis experiment and/or continuous loss of hydrogen peroxide from the electrolyte through the standard disproportionation to water and oxygen (described by the equation H20 2 = H2O + O2) which is known to be catalysed by alkaline solutions and the presence of ammonia. The lower yield in the BAS-IL electrolyte is also concordant with this due to the much higher free amine content in this electrolyte.

[0077] In order to investigate the longer term stability of the hydrogen peroxide in the

BAS electrolyte, the concentration of H20 2 was determined at various time intervals after electrochemical oxidation was complete. It can be seen from Figure 3 that the concentration of H2O2 in the BAS electrolyte drops steadily over the course of 24 hours with some amount present even after 40 hours. When a small amount of manganese dioxide (which is a known catalyst for the disproportionation reaction) was added to the

mixture, the amount of H20 2 drops significantly within first fe hours and is negligible after 18 hours.

[0078] The use of electrochemically prepared hydrogen peroxide as an oxidant was confirmed using standard test with diphenylamine as an indicator. The UV-Visible spectra of the electrolytes are shown in Figure 4. It can be seen that presence of hydrogen peroxide leads to oxidation of diphenylamine and formation of violet diphenylbenzedine (III).

[0079] Thermodynamics of hydrogen peroxide production in amine electrolytes.

[0080] Importantly the potentials involved in the processes in Figure 1 are lower than the normally expected equilibrium potential for the H20/H 20 2 reaction at pH 10. However, the results obtained clearly support the hypothesis that the electrolyte solvation is a critical aspect of the reaction in this case. It appears that the solvation is sufficient to lower the E0 to the range studied i Figure 1. This is not an unusual event - electrolyte solvation is capable of shifting redox potentials by as much as 1 V for example in the case of Au/(Au(lll).

[0081] The over potential for this process on the catalyst can be expected to be less than the full 4e H 0/0 2 process. In fact the high overpotentials required for water oxidation over many catalysts are a result of mechanisms that proceed via peroxy intermediates. In the present case a solvated form of hydrogen peroxide becomes the main product because the solvation process carries if away from the electrode into the bulk.

[0082] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[0083] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

[0084] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures.

[0085] "Comprises/comprising" and "includes/including" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', 'includes', 'including' and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". CLAIMS

1. A process for electrolysis comprising a cathode and an anode comprising a catalyst, both the cathode and anode at least partly immersed in an electrolyte, the process characterised in that the electrolyte at least partly inhibits further oxidation of a product formed at the anode.

2 . A process according to claim 1 when used for electrolytic generation of hydrogen peroxide, wherein the process comprises the step of passing a current between the cathode and the anode comprising a catalyst, both the cathode and anode being at least partly immersed in an electrolyte comprising strongly proton-accepting species.

3 . A process according to claim 1 when used for electrolytic generation of radicals for hydrogen peroxide formation, wherein the process comprises the step of passing a current between the cathode and the anode comprising a catalyst, both the cathode and anode being at least partly immersed in an electrolyte comprising a strongly proton- accepting species.

4 . A process according to any one of claims 1 to 3 wherein the electrolyte comprises a solvent and one or more dissolved species comprising a strongly proton accepting species.

5 . A process according to claim 4 wherein the electrolyte also comprises an ionic component.

6. A process according to claim 1 when used for water oxidation.

7 . A process according to claim 1 when used for water splitting.

8 . A process when used for electrolytic generation of hydrogen peroxide, wherein the process comprises the step of passing a current between the cathode and the anode comprising a catalyst, both the cathode and anode being at least partly immersed in an electrolyte comprising a strongly proton-accepting species. 9 . A process according to claim 8 wherein the electrolyte comprises a solvent and one or more dissolved species comprising a strongly proton accepting species.

0. A process according to claim 9 wherein the electrolyte also comprises an ionic component.

11. A process according to any one of the preceding claims wherein the catalyst comprises:

• one or more metal-(Group Vlb) semiconductors, and

• one or more metal-(GroupVlb))-phosphorous species.

12. A process according to claim 1 wherein the metal-(Group Vlb) semiconductor corresponds to the formula MmAa wherein;

• M is a metal,

• A is a Group Vlb species, and

• m and a have a value of between 1 and 5 .

13. A process according to claim 11 wherein the metal-(Group Vlb)-phosphorous species corresponds generally to the formula M'mA'a Py wherein:

• ' is a metal and may be the same as M,

• A' is a Group Vlb species and may be the same as A,

• m, m a and a' have a value of between 1 and 5,

• P is a phosphorous species, and • y has a value 0< y <5.

14. A process according to claim 12 or claim 3 wherein the metal is chosen from the group comprising Ti, Mo, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ir, Cd, In, Sn and the rare-earth metals or combinations thereof.

15. A process according to claim 12 or claim 13 wherein the Group VIb species is chosen from the group comprising oxygen, sulphur, selenium and tellurium.

INTERNATIONAL SEARCH REPORT International application No. PCT/AU2013/000232

A . CLASSIFICATION OF SUBJECT MATTER C25B 1/02 (2006.01) C25B 1/30 (2006.01) C25B 11/06 (2006.01) C01B 3/00 (2006.01) C01B 15/01 (2006.01)

According to International Patent Classification (IPC) or to both national classification and IPC B . FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols)

Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched

Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) EPODOC and WPL/IC/CN C25B 1 OR C25B 11 OR C 0 1B3 OR C01B 15 OR B 0 1J23 and Keywords (H202, (HYDROGEN W PEROXIDE), (ANOD+ 5D CATALYST+)) & like terms; WPI, EPODOC, TXTUS5, TXTUS4, TXTUS3, TXTUS2, TXTUS 1, TXTUSO, TXTWOl, TXTEP1, TXTCA1 , TXTAU1, TXTGB 1 and Keywords ((PRODUC+ 4D HYDROGEN PEROXIDE), (LIQUID 4D ELECTROLYTE), (CATALYST 6D ANODE)) & like terms; EPODOC and WPL/IC/CN C25B OR C01B3 OR C01B 15 OR B01J23 and Keywords ((SOLUTION 4D ELECTROLYTE), (PRODUC+ 4D HYDROGEN PEROXIDE)) & like terms.

C. DOCUMENTS CONSIDERED TO BE RELEVANT

Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No.

Documents are listed in the continuation of Box C

Further documents are listed in the continuation of Box C X See patent family annex

* Special categories of cited documents: "A" document defining the general state of the artwhich is not "T" later document published after the international filing date or priority date and not in considered to be of particular relevance conflict with the application but cited to understand the principle or theory underlying the invention "E" earlier application or patent ut published on or after the "X" document of particular relevance; the claimed invention cannot be considered novel international filing date or cannot be considered to involve an inventive step when t e document is taken alone "L" document which may throw doubts on priority claim(s) or "Y" document of particular relevance; the claimed invention cannot be considered to which is cited to establish the publication date of another involve an inventive step when the document is combined with one or more other citation or other special reason (as specified) such documents, such combination being obvious to a person skilled in the art "0" document referring to an oral disclosure, use, exhibition or other means "&" document member of the same patent family "P" document published prior to the international filing date

Date of the actual completion of the international search Date of mailing of the international search report 9 May 2013 09 May 2013 Name and mailing address of the ISA/AU Authorised officer

AUSTRALIAN PATENT OFFICE John Deuis PO BOX 200, WODEN ACT 2606, AUSTRALIA AUSTRALIAN PATENT OFFICE Email address: [email protected] (ISO 9001 Quality Certified Service) Facsimile No.: +61 2 6283 7999 Telephone No. 0262832146

FormPCT/ISA/210 (fifth sheet) (July 2009) INTERNATIONAL SEARCH REPORT International application No. C (Continuation). DOCUMENTS CONSIDERED TO BE RELEVANT PCT/AU2013/000232

Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No.

US 2002/0153262 A l (Uno et al.) 24 October 2002 X See the abstract; para. [0018]-[0025], [0036], [0074]; figure 1; and claims 1-3. 1-12, 14-15

US 2003/0019758 A l (Gopal) 30 January 2003 X See the abstract; para. [0003], [0024], [0054]; and claims 1-36. 8

US 2009/017893 1 A l (Faita) 16 July 2009 X See the abstract; para. [0026]-[0030]; and figures 1-4. 8-10

WO 2012/085 174 Al (SOLVAY SA) 28 June 2012 A See whole document. 1, 8

FormPCT/ISA/210 (fifth sheet) (July 2009) INTERNATIONAL SEARCH REPORT International application No. PCT/AU2013/000232

Box No. II Observations where certain claims were found unsearchable (Continuation of item 2 of first sheet)

This international search report has not been established in respect of certain claims under Article 17(2)(a) for the following reasons:

1. I I Claims Nos.: because they relate to subject matter not required to be searched by this Authority, namely:

2 . Q Claims Nos.: because they relate to parts of the international application that do not comply with the prescribed requirements to such an extent that no meaningful international search can be carried out, specifically:

3. I I Claims Nos: because they are dependent claims and are not drafted in accordance with the second and third sentences of Rule 6.4(a)

Box No. Ill Observations where unity of invention is lacking (Continuation of item 3 of first sheet)

This International Searching Authority found multiple inventions in this international application, as follows:

See Supplemental Box for Details

1. As all required additional search fees were timely paid by the applicant, this international search report covers all searchable claims. As all searchable claims could be searched without effort justifying additional fees, this Authority did not invite payment of additional fees. As only some of the required additional search fees were timely paid by the applicant, this international search report covers only those claims for which fees were paid, specifically claims Nos. :

No required additional search fees were timely paid by the applicant. Consequently, this international search report is restricted to the invention first mentioned in the claims; it is covered by claims Nos. :

Remark on Protest | | The additional search fees were accompanied by the applicant's protest and, where applicable, the payment of a protest fee.

I I The additional search fees were accompanied by the applicant's protest but the applicable protest fee was not paid within the time limit specified in the invitation.

I I No protest accompanied the payment of additional search fees.

FormPCT/ISA/210 (third sheet) (July 2009) INTERNATIONAL SEARCH REPORT International application No. PCT/AU2013/000232 Supplemental Box

Continuation of: Box III This International Application does not comply with the requirements of unity of invention because it does not relate to one invention or to a group of inventions so linked as to form a single general inventive concept.

This Authority has found that there are different inventions based on the following features that separate the claims into distinct groups:

• Independent claim 1 and dependent claims are directed to process for electrolysis comprising a cathode and an anode comprising a catalyst, both the cathode and anode at least partly immersed in an electrolyte, the process characterised in that the electrolyte at least partly inhibits further oxidation of a product formed at the anode. The feature of process for electrolysis is specific to this group of claims.

• Independent claim 8 and dependent claims are directed to a process when used for electrolytic generation of hydrogen peroxide, wherein the process comprises the step of passing a current between the cathode and the anode comprising a catalyst, both the cathode and anode being at least partly immersed in an electrolyte comprising a strongly proton-accepting species. The feature of a process for electrolytic generation of hydrogen peroxide is specific to this group of claims.

PCT Rule 13.2, first sentence, states that unity of invention is only fulfilled when there is a technical relationship among the claimed inventions involving one or more of the same or corresponding special technical features. PCT Rule 13.2, second sentence, defines a special technical feature as a feature which makes a contribution over the prior art.

When there is no special technical feature common to all the claimed inventions there is no unity of invention.

In the above groups of claims, the identified features may have the potential to make a contribution over the prior art but are not common to all the claimed inventions and therefore cannot provide the required technical relationship. The only feature common to all of the claimed inventions and which provides a technical relationship among them is a process of electrolysis comprising an cathode and anode partly immersed in an electrolyte, wherein the anode comprises a catalyst. However this feature does not make a contribution over the prior art because it is disclosed in:

U S 2009/0178931 A l (Faita) 16 July 2009

Therefore in the light of this document this common feature cannot be a special technical feature. Therefore there is no special technical feature common to all the claimed inventions and the requirements for unity of invention are consequently not satisfied aposteriori.

FormPCT/ISA/210 (Supplemental Box) (July 2009) INTERNATIONALSEARCH REPORT International application No. Information on patent family members PCT/AU2013/000232 This Annex lists known patent family members relating to the patent documents cited in the above-mentioned international search report. The Australian Patent Office is in no way liable for these particulars which are merely given for the purpose of information.

Patent Document/s Cited in Search Report Patent Family Member/s

Publication Number Publication Date Publication Number Publication Date

US 2002/0153262 Al 24 Oct 2002 DE 10216860 Al 24 Oct 2002 JP 20023 17287 A 31 Oct 2002 US 2002153262 Al 24 Oct 2002 US 6767447 B2 27 Jul 2004

US 2003/0019758 Al 30 Jan 2003 US 2003019758 Al 30 Jan 2003 US 6712949 B2 30 Mar 2004 WO 03010360 Al 06 Feb 2003

US 2009/0178931 Al 16 Jul 2009 AU 2007299205 Al 27 Mar 2008 AU 2007299205 B2 0 1 Sep 201 1 CA 2664202 Al 27 Mar 2008 EP 2064367 Al 03 Jun 009 IT MI20061799 Al 22 Mar 2008

US 200917893 1 Al 16 Jul 2009 WO 2008034634 Al 27 Mar 2008

WO 2012/085 174 A l 28 Jun 2012 EP 2468398 Al 27 Ju 2012 WO 2012085174 Al 28 Jun 012

End of Annex

Due to data integration issues this family listing may not include 10 digit Australian applications filed since May 2001 FormPCT/ISA/210 (Family Annex)(July 2009)