Photocatalytic water splitting using Pt-loaded visible light-responsive TiO2 thin film photocatalysts

Visible light-responsive TiO2 (Vis-TiO2) 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 TiO2 thin films. These Pt-loaded Vis-TiO2 thin films were found to decompose water involving methanol (H-2 production reaction from H2O) or 0.05 M silver nitrate solution (O-2 production reaction from H2O) under visible light (lambda >= 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-TiO2 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 H2O could be successfully achieved using an H-type glass container even under visible light. (c) 2006 Elsevier B.V. All rights reserved.