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 (r(CO2)) of the TiO2/CeO2 nanocomposite with the Ti/Ce molar ratio of 0.108 under the synergetic photothermocatalytic condition is 364 times higher than its r(CO2) 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.