Enhanced photocatalytic removal of ozone by a new chlorine-radical-mediated strategy

In this study, the photocatalytic chlorine-radical-mediated reaction dramatically enhanced the catalytic activity of TiO2 for ozone removal, which was different from traditional photocatalytic mechanism driven by hydroxyl radicals. Chlorinated TiO2 was prepared using the sol-gel method and modified through surface chlorination. The ozone-removal efficiency was up to 99.9% over the chlorinated TiO2 under UV light, which was 2.5 times that of bare TiO2. Moreover, experiments also showed that chlorinated TiO2 possessed excellent water-resistance and reusability. Characterization results unveiled that the chlorine is attached to the surface of TiO2 in the form of Ti–Cl bonds, which can capture holes to form·Cl. Subsequently, it was proven that the chain transfer reaction initiated by·Cl was mainly responsible for the remarkable improvement in the photocatalytic conversion of ozone. This new photocatalytic mechanism driven by chlorine radical opens up a new field of ozone removal by photocatalysis.