Improving the visible light photocatalytic activity of nano-sized titanium dioxide via the synergistic effects between sulfur doping and sulfation

S-doped and sulfated nano-sized TiO2 photocatalysts were prepared by a low-temperature solvothermal method, using potassium persulfate as sulfur source. The obtained samples were characterized by XRD, UV-vis DRS, FTIR, FTIR-pyridine, XPS, and nitrogen adsorption-desorption methods. Compared with undoped TiO2, the S-doped and sulfated TiO2 photocatalysts exhibited much higher photocatalytic activity for phenol degradation under visible light irradiation. It was revealed that S was not only incorporated into the crystal lattice of TiO2 replacing Ti4+ (as S4+) but also anchored on its surface in the form of SO42-. Further study indicated that there are synergistic effects between doped S and anchored SO42- on improving the visible light photocatalytic activity of TiO2. The doped S can form an impurity level below the conduction band of TiO2, extending the light response of TiO2 into visible light region, while SO42- anchored on TiO2 surface is favorable for trapping photo-induced electrons, suppressing the recombination of electrons and holes and consequently promoting the formation of hydroxyl radical. (C) 2012 Elsevier B.V. All rights reserved.