Low-temperature Preparation of TiO_2/SnO_2 Composite Film and Its Photocatalytic Activity

TiO_2/SnO_2 composite films were prepared on a slide glass with a sol-gel method at low temperature.The influence of different dip-coating times of SnO_2 layers on the photocatalytic activity of TiO_2/SnO_2 composite films was investigated.In addition,the mechanism of the photocatalytic activity enhancement of TiO_2/SnO_2 composite film was also analyzed.The results show that the photocatalytic efficiency of TiO_2 film is enhanced by using SnO_2 layer as a substrate.Since the conduction band(CB) of SnO_2 is lower than that of TiO_2,and the valence band(VB)of SnO_2 is higher than that of TiO_2, electrons transfer from TiO_2 to SnO_2,while holes oppositely diffuse into the SnO_2 layer.Thus,the charge recombination is suppressed more efficiently,and more holes can reach the TiO_2 surface to cause oxidation reaction.This is believed to be the main reason for the photocatalytic activity enhancement of the TiO_2 film photocatalyst.