Photocatalysis of La/TiO2-SiO2 thin films

La/TiO2-SiO2 thin films were prepared by sol-gel processing. The photocatalysis of the films was characterized by means of photocatalytic degradation of methylene blue under UV irradiation. The microstructures of prepared films were characterized by using XRD, FE-SEM and AFM analysis. The results show that La3+ doping can significantly improve the photocatalysis of the composite film. The best proper La doping content is 5%, and the degradation rate of La/TiO2-SiO2 is increased by 23%, higher than that before La doping. The main reason is that La3+ makes TiO2 grain size smaller, which leads to the increase of the specific area of TiO2, resulting in the higher oxidation-reduction potential of the film. Meanwhile cation vancacies with negative charge are generated when some La3+ replace Ti4+, which makes TiO2 surface charge out of the balance, and raises separation efficiency of photoelectron-hole pairs, thus improving the photocatalysis of the composite film.