Cationic S-doped TiO2/SiO2 visible-light photocatalyst synthesized by co-hydrolysis method and its application for organic degradation

Cationic S-doped TiO2 (S-TiO2)/SiO2 photocatalyst with visible-light response was synthesized by a simple co-hydrolysis method with thiourea (CH4N2S) as sulfur source and tetraethoxysilane (TEOS) as Si source. The catalytic activity was evaluated through degradation of nitrobenzene, p‑chlorophenol, and phenol under ultraviolet, artificial visible and solar light irradiations. The separability of S-TiO2/SiO2 catalyst was determined by gravity sedimentation. XPS, FTIR, TEM, UV-Vis DRS, XRD, PL, and N2 adsorption-desorption isotherms were used for the characterizations of S-TiO2/SiO2. The results showed that S-TiO2/SiO2 with appropriate S doping displayed excellent activity under ultraviolet, artificial visible and solar light irradiations, was easily separated from contaminants, and had good reusability. The added sulfur source was incorporated in the lattice of TiO2 by partially replacing Ti4+ ions at the cationic site. TiO2 with S6+ doping formed a structure with new energy levels above the valence band of TiO2 to extend the adsorption edge to 400-550 nm and to increase the surface hydroxyl amount of TiO2. New bonding between the SiO2 and TiO2 was formed to avoid the TiO2 removal during the waste water treatment. The performance of our S-TiO2/SiO2 catalyst guarantees its great practical application for the organic pollutant-contaminated waste water treatment.