The Preparation of Visible Light-Responsive TiO{sub}2 Thin Films by Applying a RF-Magnetron Sputtering Deposition Method and their Photocatalytic Reactivity for the Decomposition of Water with a Separate Evolution of H{sub}2 and O{sub}2

摘要

TiO{sub}2 (Vis-TiO{sub}2) thin films absorbing UV and visible light in regions of 250-600nm have been successfully developed by applying a radio-frequency (RF) magnetron sputtering deposition method. SIMS depth profiles of Vis-TiO{sub}2 revealed that the O/Ti ratio gradually decreases from the top surface (O/Ti ratio : 2.00 ± 0.01) to the inside (1.93 ± 0.01). This unique declined O/Ti composition (anisotropic structure) may be the origin of the significant perturbation in the electronic structure of Vis-TiO{sub}2, enabling the absorption of visible light and their high photocatalytic performance under visible light irradiation. In fact, it was found that the separate evolution of H{sub}2 and O{sub}2 from water could be successfully achieved under visible light or solar light irradiation by applying these thin film photocatalysts in an H-type glass container separating the two aqueous solutions by a TiO{sub}2 thin film and proton-exchange membrane, having H{sub}2 evolution from Pt side and O{sub}2 evolution from TiO{sub}2 thin film side, respectively.