Photocatalytic water splitting on visible light-responsive TiO2 thin films prepared by a RF magnetron sputtering deposition method

The development of visible light-responsive TiO2 (Vis-TiO2) thin films has been achieved by applying a radio-frequency magnetron sputtering deposition (RF-MS) method. Pt-loaded Vis-TiO2 thin films act as photocatalysts to decompose water involving sacrificial reagent such as methanol or silver nitrate even under visible light (lambda >= 420 nm) irradiation. It was also found that Pt-loaded Vis-TiO2 thin films decompose pure water into H-2 and O-2 stoichiometrically under light irradiation of wavelengths longer than 390 nm. Vis-TiO2 thin films exhibit columnar structures perpendicular to the substrate and a declined composition of the O/Ti ratio from the surface (O/Ti = 2.00) to bottom (O/Ti = 1.93). This unique structure (anisotropic structure) of Vis-TiO2 can be considered an important factor in the modification of the electronic properties of Vis-TiO2 thin films, enabling the absorption of visible light. Furthermore, the effect of the Pt loadings on the photocatalytic activity of the TiO2 thin films was investigated and the optimum Pt loading was determined to be 21 mu g/cm(2) as Pt metal.