Solar hydrogen production by water splitting using TiO2 based photoelectrodes

Photoelectrochemical water splitting into H-2 and O-2 was investigated using TiO2 based photoelectrodes. First, influence of photoelectorde structure on water splitting was studied through photocurrent observation. Solar energy conversion efficiency to H-2 (STH) of mesoporous TiO2 photoelectode, composed of anatase TiO2 particles of 20nm in diameter, with 10 mu thickness on FTO glass was 0.32% under 0.4V vs RHE, producing 0.39mA/cm(2). The quantum efficiency of water splitting at 360nm was 27%. Then, visible light absorbing mesoporous N-doped and S-doped anatase TiO2 photoelectrodes were studied. Visible light absorbing properties of these photoelectrodes were dramatically decreased with increasing calcination temperature to 550 degrees C. However, photocurrent such as 1 mu A/cm(2) was observed under 0.94V vs RHE and visible light irradiation using 300W-Xe lamp with 410nm cut off filter. Overall photocurrent of N-doped and S-doped TiO2 photoelectrode was about 1/5 to 1/10 of that of non-doped TiO2 photoelectrodes. Finally, solar hydrogen production by a tandem cell, composed of a mesoporous TiO2 based photoelectrode, a Pt wire electrode and a Black dye-sensitized solar cell, was studied. STH of a non-doped TiO2 photoelectrode system was 0.53% but STH of a S-doped TiO2 photoelectrode system was 0.15%, which was 1/3 lower than that of a non-doped TiO2 photoelectrodes.