Abstract: 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.

Key words: La doped, TiO₂-SiO₂ thin film, sol-gel, photocatalysis