Oxygen Vacancy-Mediated Exciton Effect in Hierarchical BiOBr Enables Dichotomy of Energy Transfer and Electron Transfer in Photocatalysis

摘要

Using solar energy through green and simple artificial photosynthesissystems are considered as a promising way to solve the energy and environmentalcrisis. However, one of the important primary steps of photosynthesis,i.e., energy transfer, is long being ignored especially in inorganicsemiconducting systems due to the small exciton binding energies. Herein,the simultaneous interrogation of the charge transfer and energy transfersteps in a photoexcitation process is proposed by utilizing few-layerednanosheet-assembled hierarchical BiOBr nanotubes with rich oxygenvacancies (OVs) as efficient multifunctional photocatalysts. Benefiting fromthe integrated 1D/2D structure and abundant OV defects, the excitonic effectstrikes a delicate balance in the optimized BiOBr photocatalyst, showingnot only improved charge carrier separation and transfer but also enhancedexciton generation. As a result, the hierarchical BiOBr nanotubes exhibithigh efficiency toward photocatalytic CO_2 reduction with an impressive COevolution rate of 135.6 μmol g~(?1) h~(?1) without cocatalyst or photosensitizer. Thedominant reactive oxygen species of singlet oxygen (~1O_2) are discriminatedfor the first time, which originated from an energy transfer process, withelectrophilic character, whereas the minor effect of superoxide anion radical(~?O_2~?) with a nucleophilic rate-determining step in the photocatalytic aerobicoxidation of sulfides.