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 CO 2 into fuels using a C 3 N 4 -based photocatalyst has shown great application potential in addressing challenges related to energy and CO 2 emission. However, this process suffers from severe charge recombination and sluggish H 2 O oxidation kinetics, resulting in low efficiency. In this study, a 2D/2D S-scheme heterojunction by combining oxygen vacancy-rich BiVO 4 nanoflakes with C 3 N 4 nanosheets (denoted as O v -BVO/CN) was fabricated to mitigate the aforementioned issues, where BiVO 4 serves as a water oxidation booster and C 3 N 4 serves as the CO 2 reduction center. By leveraging the synergistic effects of a lamellar morphology and an S-scheme charge-transfer pathway, the O v -BVO/CN heterojunction achieves efficient charge separation while maintaining maximized redox capabilities. Moreover, theoretical calculations demonstrated that the O v on the surface of BiVO 4 reverses the rate-limiting step in H 2 O oxidation while reducing its energy barrier, thereby accelerating reaction kinetics. The optimized O v -BVO/CN S-scheme heterojunction demonstrates remarkably improved photocatalytic evolution rates for CO (13.8 μmol g –1 h –1 ) and CH 4 (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 CO 2 photoreduction.