Toluene decomposition using silver vanadate/SBA-15 photocatalysts: DRIFTS study of surface chemistry and recyclability

Silver vanadate (SVO) containing SBA-15 visible-light-driven photocatalyst was synthesized using the incipient wetness impregnation procedure. X-ray diffraction (XRD) results reveal that the SVO/SBA-15 powders consisted of three kinds of phase: pure Ag4V2O7 or pure alpha-Ag3VO4 or mixed phases of Ag4V2O7 and alpha-Ag3VO4. The mass spectra indicate that the main oxidation intermediate of toluene is benzaldehyde. The sample loaded with 51 wt% SVO (51SVO/SBA-15) exhibited the best photocatalytic activity. The results of two consecutive cyclic runs and regeneration indicate that the accumulation of benzaldehyde causes an irreversible deactivation of P25, but no deactivation of 51SVO/SBA-15. The enhanced photocatalytic activity of 51SVO/SBA-15 is attributed to mixed crystalline phases of Ag4V2O7 and alpha-Ag3VO4, where alpha-Ag3VO4 is the major component. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirms the presence of Bronsted and Lewis acids on the SVO/SBA-15 composites. A favorable crystalline phase combined with high intensities of Bronsted and Lewis acids is considered the main cause of the enhanced adsorption capacity, outstanding photoactivity, and long term stability of the SVO/SBA-15 composites. (C) 2011 Elsevier B.V. All rights reserved.