Enhanced Photoresponse of Hydrogen-Modified (HM)-n-TiO_2 Thin Films for Water Splitting Reaction

摘要

Hydrogen modified n-type titanium oxide (HM-n-TiO_2) thin film photoelectrodes were synthesized by thermal oxidation of Ti metal sheet (Alfa Co. 0.25 mm thick) in an electric oven and then hydrogen was incorporated electrochemically by hydrogen evolution on it under cathodic polarization. The photoresponse of the HM-n-TiO_2 was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density j_p. The optimized electric oven-made n-TiO_2 and HM-n-TiO_2 photoelectrodes showed photocurrent densities of 0.2 mA cm~(-2) and 1.60 mA cm~(-2) respectively at measured potential of-0.4 V/Pt at illumination intensity of 100 mW cm~(-2) from a 150 Watt Xenon Lamp. This indicated an eight fold increase in photocurrent density at the same measured electrode potential. The band gap energy of HM-n-TiO_2 was found to be 2.7 eV (459 nm) and a mid-gap band at 1.67 eV (742 nm) above the valence band was observed. These HM-n-TiO_2 photoelectrodes were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM).