Preparation and Visiblelight Photo-catalytic Activity of Cr-doped TiO₂ Composite Film

Cr-TiO₂ composite films were prepared by a sol-gel and high vacuum evaporation method.The effects of Cr-doped on the microstructure,light absorption property,and photocatalytic activity of the samples were investigated.X-ray diffraction (XRD),scanning electron microscopy (SEM),and UV-vis absorption spectra (UV-vis) were used to characterize the obtained films.The photo-catalytic activity of as-prepared films was evaluated through the degradation of methylene blue.Results show that the plating layer of composite film exists as metallic Cr at 723 K and oxidized Cr₂O₃ at 823 K.The absorption edge shifted from an ultraviolet region for TiO₂ to a visible light range for annealed Cr-doped TiO₂ films.More and more Cr³⁺ diffuses into TiO₂ thin film with increasing treated temperature,which leads to intense visible-light absorption.The degradation experiments show that the maximum visible-light catalytic activity is obtained at 823 K.The degradation of methylene blue is close to 40% under visible light irradiation for 2 h.