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Sensitization of Titanium Dioxide and Strontium Titanate Electrodes By Subscriber access provided by University of Texas Libraries Sensitization of titanium dioxide and strontium titanate electrodes by ruthenium(II) tris(2,2'-bipyridine-4,4'-dicarboxylic acid) and zinc tetrakis(4-carboxyphenyl)porphyrin: an evaluation of sensitization efficiency for component photoelectrodes in a multipanel device Reza Dabestani, Allen J. Bard, Alan Campion, Marye Anne Fox, Thomas E. Mallouk, Stephen E. Webber, and J. M. White J. Phys. Chem., 1988, 92 (7), 1872-1878 • DOI: 10.1021/j100318a035 Downloaded from http://pubs.acs.org on February 2, 2009 More About This Article The permalink http://dx.doi.org/10.1021/j100318a035 provides access to: • Links to articles and content related to this article • Copyright permission to reproduce figures and/or text from this article The Journal of Physical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 1872 J. Phys Chem. 1988, 92, 1872-1878 Sensitization of Titanium Dioxide and Strontium Titanate Electrodes by Ruthenium( I I) Trls (2,2’- bipyridine-4,4’-dicar box y lic acid) and Zinc Tetrakis (4-carboxy phen yl) porphyrin: An Evaluation of Sensitization Efficiency for Component Photoelectrodes in a Muitipanei Device Reza Dabestani, Allen J. Bard, Alan Campion, Marye Anne Fox,* Thomas E. Mallouk, Stephen E. Webber, and J. M. White Department of Chemistry, University of Texas, Austin, Texas 78712 (Received: December 1. 1986; In Final Form: October 6, 1987) The utility of polycrystalline anatase Ti02 and SrTi03 semiconductor electrodes sensitized by ruthenium(I1) tris(2,2’-bi- pyridine-4,4’-dicarboxylicacid) (1) and by zinc tetrakis(4-carboxypheny1)porphyrin (2) as component photoelectrodes in a multipanel array has been evaluated. The efficiency for photocurrent generation of a single sensitized electrode is decreased as the sensitizer loading on the surface is increased beyond monolayer coverage. Power curves for both sensitizers were obtained in aqueous solutions of potassium iodide, hydroquinone, hydroquinonesulfonate (potassium salt), durohydroquinone, and potassium ferrocyanide as electron donors. From stability and efficiency considerations, hydroquinone is the most appropriate electron donor among this group. The maximum quantum efficiency attained on the metal oxide coated electrodes described herein for monochromatic excitation of 1 was 41% on Ti02 (surface coverage 3.0 X lo-’’ mol/cm2) and 57% on SrTiO, (surface coverage 5.9 X lo-’’ mol/cm2). With 2 at 420 nm a maximum quantum efficiency on Ti02 was 9.5% (surface coverage 1.7 X mol/cm2) and on SrTiO, was 27% (surface coverage 5.0 X mol/cm2). Better efficiencies were observed with adsorbed than with chemically bonded 1. The quantitative reproducibility of the observed photocurrents was a sensitive function of the preparation and porosity of the metal oxide surface. Porous Ti02gave better photoresponse than photodoped SrTiO:, as a photosensitized electrode. Despite these relatively high quantum efficiencies, the steady-state photocurrents produced on these sensitized electrodes were too low for practical operation in a multipanel device. Introduction metall~porphyrins~have been reported to sensitize metal oxides, initiating water cleavage. A recent report by Graetzel et aL6 was We have recently described a multipanel photoelectrochemical particularly encouraging, with a 44% incident photon-to-current device capable of unassisted water splitting.’ The practical utility efficiency for charge injection to TiO, from adsorbed, excited of a device constructed with Ti02/Pt photoelectrodes for solar ruthenium( 11) tris(2,2’-bipyridine-4,4’-dicarboxylicacid) reported. energy conversion is limited, however, by TiOis lack of absorption We report here quantum efficiencies for sensitization of Ti02 of visible wavelengths. This problem could be solved if an efficient and SrTi03by ruthenium(I1) tris(2,2’-bipyridine-4,4’-dicarboxylic sensitizer responsive to incident visible light could be identified. acid) (1) and zinc tetrakis(4-carboxypheny1)porphyrin (2), the Spectral sensitization of wide-band-gap semiconductors has been the subject of intensive investigation in recent years.2 Chro- mophores such as xanthene dyes,, ruthenium complexes: and (1) (a) Smotkin, E.; Bard, A. J.; Campion, A.; Fox, M. A.; Mallouk, T.; Webber, S. E.; White, J. M. J. Phys. Chem. 1986, 90, 4604. (b) Smotkin, E.; Cervera-March, S.;Bard, A. J.; Capion, A,; Fox, M. A,; Mallouk, T.; 1 1987, 91, 6. Webber, S. E.; White, J. M. Ibid. COOH (2) (a) Gerischer, H.; Michel-Beyerle, M. E.; Rebentrost, F.; Tributsch, H. Electrochim. Acta 1968, 13, 1509. (b) Tributsch, H. Ber. Bunsen.-Ges. 2 Phys. Chem. 1969,73,582. (c) Nemba, S.; Hishiki, Y. J. Phys. Chem. 1965, 69, 724. (d) Gerischer, H. In Physical Chemistry: An Advanced Treatise; (4) (a) Fujihira, M.; Oshihi, N.; Osa, T. Narure (London) 1977, 268, 226. Academic: New York, 1970; Vol. IX A. (e) Tributsch, H.; Calvin, M. (b) Spitler, M. T.; Calvin, M. J. Chem. Phys. 1977, 66,4294. (c) Andersson, Photochem. Photobiol. 1971,14,95. (f) Memming, R. Ibid. 1972, 16, 325. S.; Constable, E. C.; Dare-Edwards, M. P.; Goodenough, J. B.; Hamnett, A,; (g) Memming, R.; Tributsch, H. J. Phys. Chem. 1971, 75,565. (h) Fujishima, Seddon, K. R.; Wright, R. D. Nature (London) 1979, 280, 571. (d) Fan, F. A.; Watanabe, T.; Tatsuki, 0.;Honda, K. Chem. Left.1975.13. (i) Gerischer, R.; Bard, A. J. J. Am. Chem. SOC.1979, 101, 6139. (e) Dare-Edwards, M. H. Photochem. Photobio?. 1975, 16, 243. (j) Matsumura, M.; Nomura, Y.; P.; Goodenough, J. B.; Hamnett, A.; Seddon, K. R.; Wright, R. D. Faraday Tsubomura, H. Bull. Chem. SOC.Jpn. 1976, 49, 1409. (k) Clark, W. D. K.; Discuss. Chem. Soc. 1980, No. 70, 285. (f) Giraudeau, A,; Fan, F. R.; Bard, Sutin, N. J. Am. Chem. Soc. 1977,99,4676. (I) Hamnett, A,; Dare-Edwards, A. J. J. A. Chem. SOC.1980, u02, 5137. (8) Hishimoti, K.; Kawai, T.; Sakata, M. P.; Wright, R. D.; Seddon, K. R.; Goodenough, J. B. J. Phys. Chem. 1979, T. Nouu. J. Chim. 1983, 7, 249. (h) Matsumura, M.; Mitsuda, K.; Yoshi- 82. 3280. (m) Memming, R. Surf Sic. 1980, 101, 551. (n) Turasaki, T.; zaura, N.; Tsubormua, H. Bull. Chem. SOC.Jpn. 1981, 54, 692. (i) Duon- Sawada, T.; Kamada, H.; Fujishima, A’.; Honda, K. J. Phys. Chem. 1979,83, ghong, D.; Serpone, N.; Graetzel, M. Helu. Chim. Acta 1984, 67, 1012. (j) 2142. Krishnan, M.; Zhang, Bard, A. J. J. Am. Chem. SOC.1984,106, Gulino, D. A,; Drickamer, H. G. J. Phys. Chem. 1984,88, 1173. (k) Serpone, (0) X.; N.; Pelizzetti, E.; Graetzel, M. Coord. Chem. Rev. 1985, 64, 225. (1) Wa- 7371, and references cited therein. (p) Chang, B. T.; Campet, G.; Claverie, tanabe, T.; Fujishima, A,; Honda, K. In Energy Resources Through Photo- J.; Hangenmuller, P. Bull. Chem. SOC.Jpn. 1984, 57, 2574. (9) Wrighton, chemistry and Catalysis; Graetzel, M., Ed.; Academic: New York, 1983; and M. S.; Ellis, A. B.; Wolczanski, P. T.; Morse, D. L.; Abrahamson, H. B.; references cited therein. (m)Furlong, D. N.; Wells, D.; Sasse, H. F. J. Phys. Ginley, D. S. J. Am. Chem. SOC.1976, 98, 2774. (r) Odekirk, B.; Blakemore, Chem. 1986, 90, 1107. J. S. J. Electrochem. Soc. 1983, 130, 321. (5) (a) Breddels, P. A,; Blasse, G. Chem. Phys. Lett. 1981, 79, 209. (b) (3) (a) Kalyanasundaram, K.; Dung, D. J. Phys. Chem. 1980,84, 2551. Borgarello, E.; Kalyanasundaram, K.; Okuno, Y.; Graetzel, M. Helu. Chim. (b) Chang, M. S.; Bolton, J. R. Phofochem. Photobiol. 1981, 34, 537. (c) 4cta 1981, 64, 1937. (c) Shimidzu, T.; Iyoda, T.; Koide, Y.;Kanda, N. Nouu. Misawa, H. H.; Sakuragi, Y. Usui; Tokumaru, K. Chem. Left. 1983, 1021. J. Chim. 1983,7,21. (d) Fendler, J. H. J. Phys. Chem. 1985,89,2730, and (d) Hashimoto, K.; Kawai, T.; Sakata, T. Ibid. 1983, 709. (e) Mau, A. W.; references cited therein. (e) Kamat, P. V.; Chauvet, J. P.; Fessenden, R. W. Johansen, 0.;Sasse, W. H. F. Photochem. Photobiol. 1985, 41, 503. (f) Ibid. 1986, 90, 1389. Shimidzu, T.; Iyodo, T.; Koide, Y.J. Am. Chem. SOC.1985, 107, 35. (8) (6) Desilvestro, J.; Graetzel, M.; Kavan, L.; Moser, J.; Augustynski, J. J. Sonntag, L. P.; Spitler, M. T. J. Phys. Chem. 1985, 89, 1453. Am. Chem. SOC.1985, 107, 2988. 0022-3654/88/2092-1872$01.50/0 0 1988 American Chemical Society Component Photoelectrodes in a Multipanel Device The Journal of Physical Chemistry, Vol. 92, Na. 7, 1988 1873 effect of sensitizer loading on the observed efficiences, and power creasing coarseness (180, 240, 400, and 600 mesh, respectively) curves for several different electron donors. Finally, we evaluate and precleaned in 1:1:50 solution of HF/HN03/H20. SrTiO, the feasibility of constructing a multipanel system from several was prepared by a modified general method for mixed oxides." such sensitized metal oxide panels in an array for photoinduced To 100 mL of hot ethylene glycol (110 "C) was carefully added water splitting. 5 mL of titanium(1V) isopropoxide (0.018 mol; Alfa; 95%), I dropwise and with constant stirring. The mixture became slightly Experimental Section turbid after each added drop but turned clear upon stirring. The Materials. Ruthenium(I1) tris(2,2'-bipyridine-4,4'-dicarboxylic addition having been completed, 25 g of citric acid (0.12 mol) acid) (PF,), (1) was synthesized by the method of Whitten et a].' was slowly introduced into the hot mixture, producing a yellow A 3: 1 molar ratio of 2,2'-bipyridine-4,4'-dicarboxylic acid and solution. Finally 3.6 g of Sr(NOJ2 (0.017 mol) was carefully anhydrous ruthenium trichloride in 2-propanol was heated under added to this mixture. The resulting solution was used to wet the reflux for 7 days under argon. Water was then added to the hot titanium rod, which was then baked at 650 "C (open air) for 5-10 mixture and the solution was filtered.
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