B doped Bi2O2CO3 hierarchical microspheres: Enhanced photocatalytic performance and reaction mechanism for NO removal

Challenges are remaining in preparation of photocatalysts with efficient separation of charge carriers and utilization of visible light, and understanding of the reaction mechanism. In this work, B-doped Bi2O2CO3 hierarchical microspheres were prepared by one-step hydrothermal treatment using bismuth citrate and sodium tetraborate as precursors. Compared with pure Bi2O2CO3, the B-doped Bi2O2CO3 exhibited high visible-light photocatalytic activity of removing NO to achieve efficient air purification. Combined with experiments and DFT calculations, the doped-B could induce the formation of the intermediate level near the valence band, thus increasing the visible light absorption. The B-doping could also promote the separation of electron-hole pairs and enhance the activation of reactants. Therefore, plentiful reactive could be generated and detected by ESR via the reaction between the activated small reactant molecules and separated photogenerated carriers. To reveal the reaction mechanism of photocatalytic NO oxidation, the in-situ DRIFTS method was used to study the reaction processes, and an important intermediate NO2+ was found. The presence of NO2+ participated in the reaction enabled favorable formation for the final product of nitrates. This work could provide a new strategy for the improvement of photocatalytic efficiency.