Enhanced photocatalytic activity of titania–silica mixed oxide prepared via basic hydrolyzation

Two different synthesis routes were applied to prepare TiO2–XSiO2 (X denotes mol% of silica in titania–silica mixed oxides) with different silica concentrations by using ammonia water as hydrolysis catalyst. Through comparing the photocatalytic performance of two sets of mixed oxides, we found that the photocatalytic activity of mixed oxides prepared via the route which can promote homogeneity, was significantly enhanced as compared with that of counterparts prepared via the another route, and the highest photocatalytic activity obtained by adding about 9.1 mol% silica into titania was much higher than that of pure TiO2. The mixed oxides were investigated by means of XRD, thermal analysis, UV–vis, FT-IR and XPS. The characterization results suggest that, in comparison with pure TiO2, the mixed oxides exhibit smaller crystallite size and higher thermal stability which can elevate the temperature of anatase to rutile phase transformation due to the addition of silica. Furthermore, Brønsted acidity, which is associated with the formation of TiOSi hetero linkages where tetrahedrally coordinated silica is chemically mixed with the octahedral titania matrix, may be a very important contribution to the enhanced photocatalytic activity of titania–silica mixed oxides as well.