Accelerated Water Oxidation Kinetics Induced by Oxygen Vacancies in the BiVO4/C3N4 S-Scheme Heterojunction for Enhanced Photocatalytic CO2 Reduction

The solar-driven photocatalytic reduction of CO2 into fuels using a C3N4-based photocatalyst has shown great application potential in addressing challenges related to energy and CO2 emission. However, this process suffers from severe charge recombination and sluggish H2O oxidation kinetics, resulting in low efficiency. In this study, a 2D/2D S-scheme heterojunction by combining oxygen vacancy-rich BiVO4 nanoflakes with C3N4 nanosheets (denoted as Ov-BVO/CN) was fabricated to mitigate the aforementioned issues, where BiVO4 serves as a water oxidation booster and C3N4 serves as the CO2 reduction center. By leveraging the synergistic effects of a lamellar morphology and an S-scheme charge-transfer pathway, the Ov-BVO/CN heterojunction achieves efficient charge separation while maintaining maximized redox capabilities. Moreover, theoretical calculations demonstrated that the Ov on the surface of BiVO4 reverses the rate-limiting step in H2O oxidation while reducing its energy barrier, thereby accelerating reaction kinetics. The optimized Ov-BVO/CN S-scheme heterojunction demonstrates remarkably improved photocatalytic evolution rates for CO (13.8 μmol g–1 h–1) and CH4 (5.9 μmol g–1 h–1), which are approximately 3.8 and 3.5 times higher than those of CN nanosheets under visible-light irradiation, respectively. This work highlights the design and fabrication of highly efficient heterostructure photocatalysts for CO2 photoreduction.