Influence of the porous texture of SBA-15 mesoporous silica on the anatase formation in TiO-SiO nanocomposites

Two series of TiO 2 -SiO 2 composites have been prepared by post-synthesis impregnation of a TiO 2 precursor onto SBA-15 silica matrices and subsequent thermal treatment at 400 °C in air. The influence of the textural properties of the SBA-15 and the TiO 2 content was evaluated upon the dispersion of TiO 2 and its crystallization in anatase. The morphology of the samples before and after impregnation was observed by electronic microscopy while the textural and structural properties were evaluated by different techniques such as XRD, nitrogen sorption manometry, and Raman spectroscopy. The quantity of crystallized anatase in the composites was determined by XRD quantification using an internal standard. The bandgap energy ( E g ) of the composites was evaluated by diffuse reflectance spectroscopy and the results show that E g decreases as a function of the titania content. The photoactivity of the prepared materials was evaluated by following the degradation of methyl orange (MO) in water under UV irradiation. For the same amount of catalyst, the MO degradation rate in the presence of the composites containing 28 and 44 wt% of crystallized anatase was found to be similar to the one in the presence of commercial fully crystallized anatase. TiO 2 -SiO 2 composites with 44 wt% of anatase exhibit a better MO degradation rate than those with fully crystallized anatase.