Novel photothermocatalytic synergetic effect leads to high catalytic activity and excellent durability of anatase TiO2 nanosheets with dominant {001} facets for benzene abatement

Abstract

We studied the effect of reaction temperature on the photocatalytic activity of anatase TiO2 nanosheets with dominant {001} facets for the gas-phase photocatalytic oxidation of recalcitrant and carcinogenic benzene. It is found that the photocatalytic activity of the TiO2 nanosheets significantly enhances with increasing reaction temperature from room temperature to 240, and 290°C. Meanwhile, obvious thermocatalytic oxidation of benzene is observed on the TiO2 nanosheets in the dark when the reaction temperature increases above 240°C. The photothermocatalytic activity (CO2 production rate, rCO2-ptc) of the TiO2 nanosheets at 240 or 290°C under the irradiation of an Hg lamp is much higher than the summation of the photocatalytic activity (rCO2-pc) with the same UV light intensity at room temperature and thermocatalytic activity (rCO2-tc) at the same reaction temperature in the dark. This result indicates the presence of a photothermocatalytic synergetic effect between the photocatalysis and the thermocatalysis on the TiO2 nanosheets, thus significantly increasing the catalytic activity. The photothermocatalytic synergetic effect is further verified by in-situ FTIR spectra with CO as probe molecule: active species produced by photogenerated electrons and holes accelerate the thermocatalytic oxidation on the TiO2 nanosheets, thus significantly increasing the catalytic activity. Just by coating the sample of TiO2 nanosheets on the surface of the Hg lamp, we realized highly efficient photothermocatalytic oxidation of benzene with utilizing UV light and heating effect of infrared light from the He lamp without using additional heater. Under such photothermocatalytic condition, the photothermocatalytic activity (rCO2-ptc) of the TiO2 nanosheets increased by 42.3 times as compared to the photocatalytic activity (rCO2-pc) at room temperature with the same Hg lamp, and the TiO2 nanosheets exhibit excellent durability for benzene oxidation.