Abstract:In order to improve the photocatalytic activity of titanium dioxide (TiO2) in the visible light range, g-C3N4/TiO2 composite photocatalyst was prepared by using melamine and TiO2 at high temperature. The effect of mass ratio of melamine and TiO2, calcination temperature and time on photocatalytic activity were studied by single factor experiment. The orthogonal experiment was designed to determine the optimum preparation process that the mass ratio of melamine to TiO2 of 3.5:1, the calcination temperature of 580℃, and the calcination time of 3.5h. The degradation efficiency of nitric oxide (NO) was 74.77% under the optimum preparation condition. Then, the band structure and differential charge density of the composite system were calculated based on the first principles, and the enhancement mechanism of photocatalytic activity was analyzed by that. The results show that an internal electric field was formed between two surfaces, which prolonged the lifetime of photogenerated electrons and holes, thus, led to the enhancement of photocatalytic activity.