Understanding dual-vacancy heterojunction for boosting photocatalytic CO2 reduction with highly selective conversion to CH4

The selective reduction of carbon dioxide (CO2) as the primary component of greenhouse gas, remains a significant challenge in photocatalysis. Here, we present a novel strategy of preparing highly selective and stable heterostructure photocatalysts, which simultaneously contain oxygen and nitrogen vacancies. Synergistic catalysis effect originated from Nb2O5 with oxygen vacancies and nitrogen-rich vacancies of metal-free catalytic (g-C3N4) substrate leads to excellent photocatalytic reduction performances. The as-prepared photocatalysts exhibit outstanding capacity of selective reduction of CO2 with yields of CH4 16.07 μmol g−1 and CO 0.89 μmol g−1 after 5 cycles. Furthermore, the CO2 reduction mechanism is confirmed through density functional theory (DFT) calculation and in-situ technology in detailing. This indicates that the heterojunction surface has a lower free energy barrier for CO2 reduction compared with the pristine sample surface. This new strategy may exploit a vital application of dual-vacancy heterostructure in environmental catalysis.