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A new photoelectrode system Ti0,-ln,O, for photo-assisted electrolysis of water is described. The mixed oxide electrodes have been synthesised by solidstate sintering. These sintered electrode discs exhibited enhanced photovoltage and photocurrent of 0.78 V, 14 mA cm -' whereas for TiO, they were 0.8 V, 5 mA cm-' respectively. X-ray diffraction and scanning electron microscopy investigations of the mixed oxide electrodes have been carried out to monitor their bulk and surface characteristics. EDAX analysis has been done to explore the chemical stoichiometry. These studies indicate microcrystalline-like surface characteristics and a cation doping ('In' up to -2 % ) for the Ti0,-ln,O, electrodes. The Mott-Schottky plots (l/?-V) in 1 M NaOH solution and temperature variation of electronic conductivity (Incr-llT) for TiO, as well as Ti0,-ln,O, have been evaluated. These investigtions suggest decrease in band gap and slight shift in the flat-band potential of the mixed oxide electrode compared with TiO,. The relative enhancement in hydrogen evolution under photo-assisted mode of electrolysis of TiO, and mixed oxide (Ti0,-ln,O,) electrodes has been found to be from 1.2 to 1.8 ml h -'. The probable causes of the enhancements in photoactivity and hydrogen evolution have been suggested as:(i) 'In' cation doping in TiO, lattice;(ii) increased surface area with I n, O, inclusion;(iii) decrease in the band gap and enhanced range of absorption of mixed oxide electrode; and (iv) catalytic activity of I n, O, .

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A new photoelectrode of TiS,/TiO, alloy with a possible new TiO,S,. phase has been synthesized for the first time in the present investigation. This photoanode exhibits improved photoelectrochemical (PEC) response as compared to either TiS, or TiO, photoelectrode. With this new photoelectrode high PEC conversion efficiency is evidenced by large photovoltage (840 mv) and significantly high photocurrent density (40 mA/cm2). The photovoltage obtained in the present system is significantly high and the photocurrent density is the highest reported so far for the TiO, based systems. It has been suggested that the enhancement in photoactivity in the present system is due to the reduced band gap of TiO,S, phase in TiS,/TiO, alloy material. Such a band gap reduction is thought to be facilitated by the downward movement of the valence band of titanium disulphide which is made up of chalcogen atoms through substitution of sulphur atoms by oxygen atoms.