Improving photocatalytic activity and chlorine resistance performance of carbon nanolayer wrapped TiO2 nanocomposite catalyst for dichloromethane purification

Abstract

Developing advanced photocatalysts with excellent deep purificatation activity and robust chlorine resistance has always been the focus of attention to the photocatalytic degradation of chlorinated volatile organic compounds (CVOCs). Herein, carbon nanolayer wrapped TiO2 (CNWT-x) nanocomposites catalyst, with tunable carbon nanolayer thickness, was fabricated by controlled pyrolysis of NH2-MIL-125(Ti) to degrade dichloromethane (DCM) under UV-vis irradiation. The results demonstrated that carbon nanolayers wrapped TiO2 could drastically accelerate the transfer of photogenerated electrons and prolong photogenerated carrier lifetime, thereby producing abundant •O2− and •OH radicals with strong oxidation ability. These radicals rapidly oxidated DCM and intermediates to final products of CO2 and Cl2. The CNWT-2 sample exhibited an optimal catalytic activity with 85% DCM conversion and 90% CO2 selectivity even after 5 h UV-vis light irradiation. More importantly, CNWT-2 also presented robust resistance performance against chlorine and high humidity. Furthermore, in-situ NAP XPS results suggested that the dissociated chlorine species might preferentially be absorbed onto the stable outer carbon nanolayers, which went far towards protecting their interior TiO2 active sites. These would reduce the reaction probability of the dissociated chlorine species with TiO2 active sites and the generated organic intermediates, inhibiting the occurrence of toxic polychlorinated by-products and catalyst deactivation by chloride poisoning. This work offers a facile and efficient strategy to develop highly active and stable catalysts for the photocatalytic degradation of CVOCs.