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

We have successfully grown BiOClxBr1-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.