Effect of calcination temperature on the structure and visible-light photocatalytic activities of (N, S and C) co-doped TiO2 nano-materials

Abstract

The (N, S and C) co-doped TiO2 samples (NSC-TiO2) were synthesized by the sol–gel method combining with the high energy ball milling method calcined at the different temperature (400–700°C), employing butyl titanate as the titanium source and thiourea as the doping agent. The structures of NSC-TiO2 samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), X-ray photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The photocatalytic activities were checked through the photocatalytic reduction of Cr(VI) as a model compound under visible light irradiation. The results showed that the (N, S and C) co-doping and the calcination temperature played important role on the microstructure and photocatalytic activity of the samples. According to XPS spectra, sulfur was mainly attributed to the TiOS bond; nitrogen was ascribed to the TiON and TiN bonds; carbon was assigned to the TiOC bond in the NSC-TiO2 samples. (N, S and C) co-doped TiO2 samples calcinated at 500°C exhibits higher photocatalytic activity than that of the other samples under visible light irradiation, which can be attributed to the synergic effect of its enhancing crystallization of anatase and (N, S and C) co-doping.