Structure and photocatalytic activities of Ag/TiO2 thin films

Nanometric TiO2 thin films doped with Ag were prepared by the sol-gel method. The effects of Ag on the structure of TiO2 films were systematically studied by means of X-ray diffraction, BET nitrogen adsorption, UV-VIS-NIR transmission spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity of Ag/TiO2 thin films was characterized and studied in photocatalytic degradation of methylene blue under UV irradiation in comparison with pure TiO2 thin films. The results showed that suitable amount of Ag effectively improved photocatalytic activity of TiO2 thin films. The mechanism could be ascribed to that: (1) The electron-hole pair separation efficiency of TiO2 films was improved by the introduction of Ag. The concentration of photoholes at the surface of TiO2 films increased; (2) TiO2 particle sizes decreased while Ag was introduced, which further widened the band-gap of TiO2 and improved its photocatalytic redox capability; (3) The absorption of -OH and H2O on TiO2 films was increased, which improved the photoholes transfer efficiency and the concentration of reactive -OH group on TiO2 thin films after UV irradiation.