Visible light-responded C, N and S co-doped anatase TiO2 for photocatalytic reduction of Cr(VI)

Abstract

The (C, N and S) co-doped TiO2 (TH-TiO2) samples were synthesized by a sol-gel method calcined at 500 °C, employing butyl titanate as the titanium source and thiourea as the dopant. The structures of TH-TiO2 samples were characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectroscopy, Thermo gravimetry and differential thermal analysis (TG-DTA), 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 thiourea content played an important role on the microstructure and photocatalytic activity of the samples. According to XPS results, (C, N and S) atoms were successfully co-doped into the nanostructures of TH-TiO2 samples. TH-TiO2 samples with thiourea: Ti molar ratio of 1.5 exhibits higher photocatalytic activity than that of the other samples under visible light irradiation, which can be attributed to the synergic effect of the pure anatase structure, the higher light absorption characteristics in visible regions, separation efficiency of electron–hole pairs, the specific surface area and the optimum (C, N and S) content.