Photocatalytic Decomposition of Water on Double-Layered Visible Light-Responsive TiO2 Thin Films Prepared by a Magnetron Sputtering Deposition Method

Abstract

A radio-frequency magnetron sputtering (RF-MS) deposition method was applied to prepare a unique double-layered visible light-responsive TiO2 thin film photocatalyst on a Ti foil substrate (DL-TiO2/Ti). The DL-TiO2/Ti consists of a UV light-responsive TiO2 thin film (UV-TiO2) deposited as the inner block layer on a Ti foil substrate and a visible light-responsive TiO2 thin film (Vis-TiO2) deposited as the outer layer. DL-TiO2/Ti exhibited higher photoelectrochemical and photocatalytic performance under both UV and visible light irradiation than a single-layered Vis-TiO2 thin film photocatalyst deposited on a Ti foil substrate. The optimal thickness of the UV-TiO2 film as the inner block layer of DL-TiO2/Ti was found be 100 nm in terms of the photoelectrochemical and photocatalytic performance. Expanding on this work, a novel double-layered TiO2 thin film device, DL-TiO2/Ti/Pt, was also prepared by the RF-MS method where DL-TiO2 was deposited on one side of a Ti foil substrate and Pt was deposited on the other side. The separate evolution of H2 and O2 from H2O was successfully achieved by using an H-type glass cell consisting of two aqueous phases separated by the DL-TiO2/Ti/Pt and a proton-exchange membrane. The separate evolution rate of H2 and O2 was found to be dramatically enhanced on DL-TiO2/Ti/Pt as compared with a single-layered Vis-TiO2 thin film device under white light irradiation from a solar simulator.