Enhanced photocatalytic activity of sulfated silica-titania composites prepared by impregnation using ammonium persulfate solution

Sulfate (SO42−) modified silica–titania (SiO2–TiO2) composite photocatalysts with different loadings of SO42− were prepared by a facile pore impregnating method using ammonium persulfate (NH4)2S2O8 solution. The surface parameters, structure, morphology, the adsorption ability of light, the binding energy of Ti2p and O1s, and the formation rate of OH radicals produced during the photocatalytic reaction process were characterized by the Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and terephthalic acid photoluminescence probing technique (TA-PL), respectively. The results reveal that sulfating of SiO2–TiO2 induces the shift of Ti2p and O1s, and increases the adsorption of rhodamine B on the sulfated photocatalysts and the formation rate of OH radicals produced during the photocatalytic reaction process. The photocatalytic activity of SO42−/SiO2–TiO2 for de-colorization of rhodamine B aqueous solution was evaluated. The result shows that when wt% of SO42− is 8.6%, SO42−/SiO2−TiO2 exhibits the best photocatalytic activity under ultraviolet light irradiation and the possible reason is discussed.