In this presentation, we report construction of a novel photo electrochemical cell for generation of hydrogen using solar light. The photo anode is produced by synthesis of ordered nanotubular arrays of TiO₂ by a single step electrochemical anodization process in fluoride containing organic solutions (typically ethylene glycol). Subsequent annealing of the nanotubular arrays in hydrogen environment yields optimum volume fraction of anatase plus rutile phases and incorporation of carbon in the TiO₂ lattice. The diffusion of carbon into the TiO₂ lattice introduces defect states in the band gap and also modifies the band gap to 2.1 eV.  The nanotubular TiO₂ photo anodes formed by the anodization process show more superior charge transport properties and structural integrity than the anodes made by spray pyrolysis of nano-particles. Further, construction of very large area (active on both sides) electrode materials with uniform electronic and mechanical properties is easily achievable using the proposed electrochemical anodization process. Conventionally, a Pt sheet is used as cathode for solar water splitting. In this new cell, the Pt sheet electrode is replaced with a TiO₂ nanotubular template loaded with 3-6 nm size Pt nano-particles (0.4 mg/cm²). Nickel nano-particles loaded TiO₂ cathode also is developed. These new cathode materials have larger surface areas than the conventional electrodes, and these are much cheaper.

Photo electrochemical studies are carried out on these carbon modified double sided nanotubular TiO₂ photo anodes and Pt or Ni nano-particles loaded TiO₂ nanotubular cathodes. The surface area of the electrode is 8 cm². Photo current is recorded as a function of both applied external bias potential and light wavelength using a simulated solar light source with band pass filters. Photo current is observed at wavelengths less than 600 nm. The maximum observed photo current density using the entire solar light is 3.3 mA/cm² at 0.2 V Ag/AgCl. The maximum photo conversion efficiency using only the UV portion of the solar spectra is 13.3%. When considering only the visible portion of the solar light at 520 ± 46 nm, the maximum photo conversion efficiency is 8.5 %. Further studies are being carried out to improve the overall solar to hydrogen efficiency of the system in the entire solar spectra.