Influence of the porous texture of SBA-15 mesoporous silica on the anatase formation in TiO2–SiO2 nanocomposites

Abstract

Two series of TiO₂–SiO₂ composites have been prepared by post-synthesis impregnation of a TiO₂ 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 TiO₂ content was evaluated upon the dispersion of TiO₂ 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.