Photoinduced charge separation and simulated solar-driven photocatalytic performance of C–N-co-doped TiO2 prepared by sol–gel method

C–N-co-doped anatase TiO2 photocatalysts were successfully prepared by a sol–gel method and characterized by Brunauer–Emmett–Teller method, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope (SEM), and surface photovoltage spectroscopy (SPS). The separation efficiency of photogenerated charges was investigated using benzoquinone as scavenger. An obvious redshift of the absorption edge of TiO2 was observed owing to C and N doping. Moreover, doping C and N into TiO2 increases the content of hydroxyl content on the surface of photocatalysts and photoinduced charge separation efficiency. The photocatalytic activity was evaluated by decolorization of methyl orange (MO) aqueous solution under simulated sun light and visible light irradiation. The results show that photocatalytic activities of the TiO2 are greatly improved by C and N co-doping, which can be further confirmed by the removal of COD of MO aqueous solution. In general, the strong SPS response corresponds to the high separation rate of photoinduced charge carriers on the basis of the SPS principle. Thus, it can be confirmed that the C–, N-TiO2 sample has a higher charge separation rate than the pure TiO2 sample, and the 4 % C–, N-TiO2 shows the highest charge separation rate