Enhancement of visible light activity in Ag modified SnO2/TiO2

Ag modified SnO2/TiO2 nanoparticles were successfully prepared by a modified sol–gel method, without adding any acid or alkali. The entire preparation differs from the traditional sol–gel synthesis of TiO2 that the reaction can get controlled by adjusting the flow speed of water vapor. Ultraviolet–visible diffuse reflectance spectra (UV–vis) and spin-trapping electron paramagnetic resonance (EPR) were used to forecast the photocatalytic activity of the samples, and the results were proved by the degradation of methylene blue solution under visible light. Compared with pure TiO2, as-prepared Ag modified SnO2/TiO2 nanoparticles exhibited not only an enhanced photocatalytic activity but also an improved stability. Among all of samples, the composite with 0.5% of Ag and 1% of Sn showed the best photocatalytic performance and stability. Further increasing the Ag proportion will result in the decrease of the photocatalytic activity. A relative mechanism was proposed and discussed in detail.