Synergistic mediation of dual donor levels in CNS/BOCB-OV heterojunctions for enhanced photocatalytic CO₂ reduction

We have successfully grown BiOCl_xBr_1−x nanosheets with oxygen vacancies (BOCB-OV) on the surface of ultrathin g-C₃N₄ (CNS) to form heterostructures through a solvothermal approach that creates N-vacancies on CNS. The heterojunction formation promotes CO₂ adsorption with activation and broadens light-harvesting capabilities. Moreover, the intimate contact between CNS and BOCB-OV creates an interfacial electric field directed from CNS to BOCB-OV, facilitating separation and transfer of photogenerated charge carriers. Importantly, introduction of nitrogen/oxygen vacancies in CNS/BOCB-OV leads to new donor energy levels in the bandgap, which boosts the light absorption capacity and provides a stable pathway for charge transfer across heterojunctions. Consequently, the CNS/BOCB-OV heterostructures exhibited greatly enhanced photocatalytic activities for CO₂ reduction. Further, by combining DFT calculation and in situ FTIR characterization, the photocatalytic reaction mechanism and possible CO₂ reduction pathways are elucidated. The combination of heterostructure construction and defect engineering provides a promising strategy for developing efficient two-dimensional heterostructure photocatalysts.