The photoelectrochemical response of TiO2-WO3 mixed oxide films prepared by thermal oxidation of titanium coated with tungsten

Titanium sheets coated with vacuum-deposited tungsten films were oxidized at 1073 and 1173 K to form TiO2-WO3 mixed oxide films. The mixed oxide films showed higher anodic photocurrents than pure TiO2 films formed on Ti due to the oxidation of water. The photocurrent increased with the amount of W deposition on the Ti substrate and with oxidation temperature. From scanning electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy, it is concluded that the films containing larger amounts and uniformly distributed W in the depth direction of the film generate larger photocurrents. For WO3 films formed by thermal oxidation of W sheets, there was anodic dissolution of the underlying metal. This may be due to imperfections in the WO3 film. Such dissolution was not observed for the TiO2-WO3 mixed oxide films, showing the electrochemical stability of these films.