TiO2 electrode

The performance of the three sensitizers 22,8 and 56, which contain different degrees of protonation were studied on nanocrystalline TiO2 electrodes [80]. Figure 13 show the photocurrent action spectra obtained with a monolayer of these complexes coated on TiO2 films. 

In 1972, Fujishima and Honda 185-187) opened a new research field in heterogeneous photocatalysis with their discovery of the photocatalytic splitting of water on TiO2 electrodes. Thereafter, TiOj, in part because of its high stability and lack of... 

On the basis of Tafel slope studies and potential relaxation transients, mechanism (1) has been suggested for Cl2 evolution at Pt, whereas chlorine evolution at the technically hydrated Ru02/TiO2 electrode appears to proceed by (3) or, possibly, (4). 

W. Gissler, P. L. Lensi, and S. Pizzini, Electrochemical investigation of an illuminated TiO2 electrode, J. Appl. Electrochem. 6 (1976) 9-13. 

W. Siripala and M. Tomkiewicz, Surface recombination at n-TiO2 electrodes in photoelectrolytic solar cells, J. Electrochem. Soc. 130 (1983) 1062-1067. 

MAGARIETAL. Photooxidation Reaction of Water on an n TiO2 Electrode 299... 

Based on extensive screening of hundreds of ruthenium complexes, we discovered that the sensitizer excited-state oxidation potential should be negative and at least - 0.9 V versus saturated calomel electrode (SCE), in order to inject electrons efficiently onto the TiO2 conduction band. The ground-state oxidation potential should be about 0.5 V versus SCE, in order to be regenerated rapidly via electron donation from the electrolyte (iodide/triiodide redox system) or an hole conductor. A significant decrease in electron-injection efficiencies will occur if the excited-and ground-state redox potentials are lower than these values. 

Apart from oxides such as TiO2, ZnO, and ZrO2, sulfides (typically CdS), nio-bates, tantalates, titanates, and other compounds have been tested as photocatalytic materials for splitting water. Composites (Kida et al., 2003 Rincon et al., 2007) and porous materials (Velaski et al., 2006) have been introduced as electrode materials in photovoltaic cells in the last years. 

Photocatalytic oxidation of organic pollutants on TiO2-based materials has been extensively investigated. The catalyst is used in the form of a suspension of fine particles or thin film on robust substrates. Figure 12.2 shows the variation of open-circuit potential with time for TiO2 film electrodes, prepared by anodization of Ti... 

FIGURE 12.4 Variation of the difference photocurrent density with the bias potential for TiO2 film electrodes in contact with base solution, 0.1 and 0.5 mM salicylic acid. (Adapted from Li and Shen, 2006. J. Solid State Electrochem. 10, 980-986, with permission from Springer.)... 

Li, M.C., and Shen, J.N. 2006. Photoelectrochemical oxidation behaviour of organic substances on TiO2 thin-film electrodes. Journal of Solid State Electrochemistry 10, 980-986. 

Ma, L., Li, Y, Yu, X., Zhu, N., Yang, Q., and Noh, C.-H. 2008. Electrochemical preparation of PMeT/TiO2 nanocomposite electrochromic electrodes with enhanced long-term stability. Journal of Solid State Electrochemistry 12, 1503-1509. 

An aluminum electrode modified by a chemically deposited palladium pen-tacyanonitrosylferrate film was reported in [33]. Vitreous carbon electrode modified with cobalt phthalocyanine was used in [34]. Electrocatalytic activity of nanos-tructured polymeric tetraruthenated porphyrin film was studied in [35[. Codeposition of Pt nanoparticles and Fe(III) species on glassy-carbon electrode resulted in significant catalytic activity in nitrite oxidation [36[. It was shown that the photocatalytic oxidation at a TiO2/Ti film electrode can be electrochemically promoted [37]. 

The photoelectrochemical production of chlorine at nanocrystalline titanium dioxide thin film electrodes exposed to U V light has been reported [96]. In this process, the energy from photons substantially reduces the overpotential required for the chlorine evolution process and therefore less harsh conditions are required. Metal doping of the TiO2 photoelectrocatalyst was explored but found to be not beneficial for this process. In future, this kind of process could be of practical value, in particular, for water treatment and disinfection applications requiring low levels of chlorine. 

The structure, morphology, and photoelectrochemical properties of CdSe and CdSe Tei-x semiconductor thin films prepared by cathodic electrodeposition on Ni and Ti electrodes from acidic solution containing CdSO4, SeO2, and TiO2 were investigated [192]. 

Sene, J.J., Zeltner, W.A., and Anderson, M.A., Fundamental photoelectrocatalytic and electrophoretic mobility studies of TiO2 and V-doped TiO lliin-film electrode materials, J. Phys. Chem. B, 107, 1597, 2003. 

Among mixed oxides employed in mixed potential sensors is ITO, this having been used for both NO [291] and CO [292-294] sensors. A further example of a doped oxide being used as an electrode is TiO2, which has been doped with tantalum for hydrocarbon sensors [295] or vanadium for SO2 sensors [296]. 

K. Hirano and A. J. Bard, Semiconductor electrodes XXVIII. Rotating ring-disk electrode studies of photo-oxidation of acetate and iodide at n-TiO2, 1 Electrochem. Soc. 127 (1980) 1056-1059. 

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