Abstract: Pure and doped or co-doped TiO2 catalysts with various amounts of chromium and sulfur were obtained by the sol-gel process, in which tetrabutyl titanate was used as the precursor and chromium nitrate and thiourea as ion donors. Indigo carmine photodegradation experiments showed that the co-doped catalyst has higher photocatalytic activity than that of pure and single-doped ones. The co-doped catalyst with 0.60% (atomic ratio) chromium and 1.2% (atomic ratio) sulfur calcined at 500 ℃ has the highest catalytic efficiency under visible irradiation. The catalysts were characterized byX-raydiffraction, N2 adsorption,X-rayphotoelectron spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The results showed that the co-doped catalysts have anatase phase, higher specific area, and wide range of visible response. The higher visible light photocatalytic activity of the co-doped TiO2 is attributed to the doped chromium and sulfur. The doped chromium lowers the band gap and expands the absorption of visible light region, and the doped sulfur maintains the charge balance and enhances visible light absorption.

Key words: chromium, sulfur, co-doping, titania, visible light, photodegradation, indigo carmine