Photocatalytic water splitting using Pt-loaded visible light-responsive TiO 2 thin film photocatalysts

Abstract

Visible light-responsive TiO 2 (Vis-TiO 2) thin films which exhibit a unique declined O/Ti composition from the surface to the deep inside bulk have been successfully developed under a substrate temperature of 873 K by applying a radio-frequency magnetron sputtering deposition (RF-MS) method. By controlling the Ar gas pressure during the deposition procedure, it was possible to control the optical properties of the TiO 2 thin films. These Pt-loaded Vis-TiO 2 thin films were found to decompose water involving methanol (H 2 production reaction from H 2O) or 0.05 M silver nitrate solution (O 2 production reaction from H 2O) under visible light ( λ ≥ 420 nm) irradiation. In particular, the photo-oxidation of water to produce O 2 proceeds under visible light of wavelengths longer than 550 nm. The conduction and valence bands of Vis-TiO 2 thin film photocatalysts were, thus, seen to have enough potential for the decomposition of water into H 2 and O 2 under visible light irradiation. These thin films were found to be stable and the declined composition could be retained even after the reaction and calcination treatment at 723 K in O 2 atmosphere. Moreover, the stoichiometric and separate evolution of H 2 and O 2 from H 2O could be successfully achieved using an H-type glass container even under visible light.