Hydrothermal preparation and photocatalytic performance of N, S-doped nanometer TiO₂ under sunshine irradiation

N, S-doped TiO₂ photocatalysts at a nanometer scale were successfully prepared by hydrothermal process, and photocatalytic activity of the obtained powders for degradation of methyl orange under sunshine irradiation was studied. The products were characterized by XRD, TEM, XPS, FT-IR and UV-vis diffuse reflectance spectra. Experimental results indicate that the Nitrogen and Sulfur atoms are incorporated into the lattice of TiO₂, and they exist in the state of S⁶⁺ and substitutional or interstitial N, respectively. The incorporation was responsible for narrowing the band gap of TiO₂ and shifting its optical response from ultraviolet to the visible-light region. The 3% N, S-TiO₂ photocatalyst calcined at 500°C exhibited the highest photocatalytic activity. The degradation rate of 10mgL^-1 methyl orange solution reached approximately 92% under sunshine irradiation for 6h when the pH value of the methyl solution was 4.