Photocatalytic toluene degradation over Bi-decorated TiO₂: Promoted O₂ supply to catalyst's surface by metallic Bi

In the photocatalytic volatile organic compounds (VOCs) degradation, the accumulation of intermediate products on the surface of catalysts could cause a decrease in activity through retarding reactant (e.g. O₂) supply to surface active sites. Herein, Bi decorated TiO₂ photocatalysts (Bi/TiO₂) for photocatalytic toluene degradation were prepared and systematically studied. It is found that metallic Bi modification improves the ability of photocatalysts to capture O₂. As a result, the activities of the Bi/TiO₂ photocatalysts are obviously higher than that of the TiO₂ for photocatalytic toluene degradation, and the productions of photogenerated reactive oxygen species (^[rad]O₂⁻ and H₂O₂) over the Bi/TiO₂ photocatalysts are almost equal to that over the TiO₂ despite the fact that the separation efficiency of photoinduced charge carriers is decreased after the addition of Bi. Adsorbed benzaldehyde is the main surface intermediate on the surface of the Bi/TiO₂ photocatalysts, whereas plenty of more readily oxidized aliphatic carboxylate species was monitored on the surface of the TiO₂, which can be attributed to insufficient O₂ supply to the TiO₂ surface. This further indicates the positive role of the promoted O₂ supply by Bi in the photocatalytic toluene degradation. The present work offers a new window for addressing the catalyst deactivation in the photocatalytic VOCs degradation.