Low-temperature preparation of TiO2/SnO2 composite film and its photocatalytic activity

TiO2/SnO2 composite films were prepared on a slide glass with a sol-gel method at low temperature. The influence of different dip-coating times of SnO2 layers on the photocatalytic activity of TiO2/SnO2 composite films was investigated. In addition, the mechanism of the photocatalytic activity enhancement of TiO2/SnO2 composite film was also analyzed. The results show that the photocatalytic efficiency of TiO2 film is enhanced by using SnO2 layer as a substrate. Since the conduction band (CB) of SnO2 is lower than that of TiO2, and the valence band (VB) of SnO2 is higher than that of TiO2, electrons transfer from TiO2 to SnO2, while holes oppositely diffuse into the SnO2 layer. Thus, the charge recombination is suppressed more efficiently, and more holes can reach the TiO2 surface to cause oxidation reaction. This is believed to be the main reason for the photocatalytic activity enhancement of the TiO2 film photocatalyst.