Abstract: A WO₃/TiO₂ composite film and a pure TiO₂ film were prepared by microarc oxidation in tungsten electrolyte and phosphate electrolyte, respectively. The structure and photophysical properties of the two films were characterized by X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy, and photoluminescence. The results showed that the two films consisted of a mixture of anatase and rutile, but the ratio of anatase to rutile was different. In addition, WO₃ was present in the WO₃/TiO₂ composite film. The two films had porous structure, but more pores distributed homegeneously on the WO₃/TiO₂ composite film surface than on the TiO₂ film. The WO₃/TiO₂ composite film showed wider absorption rang while the TiO₂ film presented better optical absorption in the UV region. The photoluminescence intensity of the WO₃/TiO₂ composite film was lower than that of the TiO₂ film, which meant that the recombination of photo-generated electrons and holes in the former was less than that in the later. Compared to the TiO₂ film, the WO₃/TiO₂ composite film had higher surface acidity, which increased the adsorption of organics and OH groups on the film surface. More than 85% of rhodanmine was removed by the WO₃/TiO₂ composite film, whereas only 23% of rhodamine was removed by the TiO₂ film for 2 h. The higher photocatalytic removal ratio of the WO₃/TiO₂ composite film was ascribed to the larger specific surface area, better separation between electrons and holes, and higher surface acidity.

Key words: tungsten, titanium, microarc oxidation, electrolyte, titania film, photocatalysis