Preparation and characterization of SnO2/ZnO/TiO2 composite semiconductor with enhanced photocatalytic activity

In this study, SnO2/ZnO/TiO2 composite photocatalysts were successfully synthesized using sol–gel and solid-state methods. The as-prepared samples were characterized for the phase structure, optical absorption, thermal stability and surface property using X-ray diffraction (XRD), Raman spectroscopy, UV–vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The photocatalytic activity was tested with photodecomposition of Methyl Orange under both visible and UV light irradiations. The results indicated that the SnO2/ZnO/TiO2 composite materials have an apparent visible light absorption, combining TiO2 with SnO2 and ZnO could promote the TiO2 phase transition from anatase to rutile. The SnO2/ZnO/TiO2 heterojunctions with the highest performance was the one prepared using Sn(Zn)/Ti molar ratio of 0.05. It was found that the enhanced photocatalytic activity could be attributed to the increased separation of the charge carriers, which therefore depress the charge pair recombination and prolonged the electron lifetime in the composite structure, and a large number of electrons could take part in the photoreaction. Based on the results of the present study, a tentative mechanism for the enhanced photocatalysis of the SnO2/ZnO/TiO2 composite catalyst has been proposed.