The Photoelectrochemical Response of TiO2 ‐ WO 3 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 mixed oxide films. The mixed oxide films showed higher anodic photocurrents than pure 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 film s containing larger amounts and uniformly distributed W in the depth direction of the film generate larger photocurrents. For films formed by thermal oxidation of W sheets, there was anodic dissolution of the underlying metal. This may be due to imperfections in the film. Such dissolution was not observed for the mixed oxide films, showing the electrochemical stability of these films.