Synergetic Effect between Photocatalysis on TiO2 and Thermocatalysis on CeO2 for Gas-Phase Oxidation of Benzene on TiO2/CeO2 Nanocomposites

TiO2/CeO2 nanocomposites of anatase TiO2 nanoparticles supported on microsized mesoporous CeO2 were prepared and characterized by SEM, TEM, BET, XRD, Raman, XPS, and diffuse reflectance UV–vis absorption. The formation of the TiO2/CeO2 nanocomposites considerably enhances their catalytic activity for the gas-phase oxidation of benzene, one of the hazardous volatile organic compounds (VOCs), under the irradiation of a Xe lamp compared to pure CeO2 and TiO2. A solar-light-driven thermocatalysis on CeO2 is found for the TiO2/CeO2 nanocomposites. There is a synergetic effect between the photocatalysis on TiO2 and the thermocatalysis on CeO2 for the TiO2/CeO2 nanocomposites, which significantly increases their catalytic activity. The CO2 formation rate (rCO2) of the TiO2/CeO2 nanocomposite with the Ti/Ce molar ratio of 0.108 under the synergetic photothermocatalytic condition is 36.4 times higher than its rCO2 under the conventional photocatalytic condition at near room temperature. CO temperature-programmed reduction (CO-TPR) with the irradiation of the Xe lamp and in the dark reveals that the synergetic effect, which occurs at the interface of the TiO2/CeO2 nanocomposite, is due to the considerable promotion of the CeO2 reduction by the photocatalysis on TiO2.