The spatially separated active sites for holes and electrons boost the radicals generation for toluene degradation

Hydroxyl (⸱OH) and superoxide (⸱O₂^-) radicals are the main drivers for photocatalysis in toluene degradation, but their generation mechanisms are still ambiguous due to the lack of direct evidence. The spatially separated active sites for holes and electrons can help to clarify the dynamic process of radicals generation. By performing theoretical calculations, it is demonstrated that the spatially separated active sites for holes and electrons on the Bi₂O₂CO₃ surface can be constructed by introducing oxygen vacancies in the [Bi₂O₂]²⁺ layer. H₂O and O₂ molecules can be better adsorbed and activated at hole and electron active sites, separately. Accordingly, the pristine and defective Bi₂O₂CO₃ are prepared. The dynamic behavior of H₂O and O₂ molecules at the matching active sites is revealed, which indicates the efficient adsorption of reactants and the substantial production of radicals. Significantly, the specificity of the spatially separated holes and electrons active sites for ⸱OH and ⸱O₂^- radicals generation, respectively, is demonstrated by in situ EPR with the H₂O vapor atmosphere. This work provides a design concept for unraveling reaction mechanisms to realize controllable radicals generation.