Visible light active hydrogen modified (HM)-n-TiO2 thin films for photoelectrochemical splitting of water

Visible light active hydrogen modified n-type titanium oxide (HM-n-TiO2) thin films were synthesized by thermal oxidation of Ti metal sheet (Alfa Co. 0.25 mm thick) in an electric oven followed by incorporation of hydrogen electrochemically under cathodic polarization at −1.6 V vs Pt. The photoresponse of the HM-n-TiO2 was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen in terms of photocurrent density, Jp. The optimized electric oven-made n-TiO2 and HM-n-TiO2 photoelectrodes showed photocurrent densities of 0.2 mA cm−2 and 1.60 mA cm−2, respectively, at a measured potential of −0.4 V vs Pt at illumination intensity of 100 mW cm−2 from a 150 W xenon lamp. This indicated an eightfold increase in photocurrent density for HM-n-TiO2 compared to oven-made n-TiO2 at the same measured electrode potential. The band-gap energy of HM-n-TiO2 was found to be 2.7 eV compared to 2.82 eV for electric oven-made n-TiO2 and a mid-gap band at 1.67 eV above the valence band was also observed. The HM-n-TiO2 thin film photoelectrodes were characterized using photocurrent density under monochromatic light illumination and UV–Vis spectral measurements.