Transition metal oxides supported onto silica gel as visible light-driven photocatalysts

Supported oxides of some transition metals have been prepared via incipient wetness impregnation of a mesoporous silica. Obtained compositions have been studied using DTA-TG and XRD analysis, FTIR, Raman, UV-Vis and XPS spectroscopy as well as low-temperature nitrogen adsorption-desorption. Deposited oxides have amorphous or low-crystalline structure and exhibit electronic properties different from those for bulk oxides. Red shift of adsorption edge is observed for most supported samples compared with corresponding bulk oxides. All tested samples regardless of the band gap showed photocatalytic activity under visible irradiation in process of rhodamine B degradation. The prepared supported oxides were more active compared with bulk oxides. The dispersion of oxides on the surface of the support and the greater accessibility of dye molecules to the active sites of the surface are the main reason for this. As a result, Ag/SiO(2)and TiO2/SiO(2)samples exhibited maximal photocatalytic activity. Three mechanisms of initiation for photocatalytic process were considered.