Enhanced visible light photocatalytic activity of N, F-codoped TiO₂ powders with high thermal stability

Doping non-metals onto TiO₂ has been regarded as a promising way to gain a more effective photocatalyst. In this paper, N, F-codoped TiO₂ was synthesized by the sol-gel method, demonstrating both high adsorption capacity and high photocatalytic activity under visible light irradiation. Samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and UV-visible diffuse reflectance spectra (UV-vis DRS). The results show that N, F-codoping can reduce the impact of calcination temperature on the structure and morphology of the sample, resulting in the sample exhibiting good thermal stability, even when the calcination temperature changes in a large range, instead of rutile, the anatase around 20 nm is the only phase in N, F-codoped samples. It can be clearly observed from the SEM images that N, F-codoped samples calcined at different temperatures are in the state of scattered particles with small size and good dispersed property. And it is vivid that the absorption intensity of N, F-codoped TiO₂ samples in the visible light range increases substantially in DRS. According to the result of photocatalytic activity experiment, N, F-codoped TiO₂ samples calcined at 973 K exhibited the highest degradation rate for Methylene Blue.