Remarkable photocatalytic activity enhancement of CO2 conversion over 2D/2D g-C3N4/BiVO4 Z-scheme heterojunction promoted by efficient interfacial charge transfer

In this study, a series of dual two-dimensional (2D/2D) Z-scheme g-C3N4/BiVO4 ultrathin nanosheets were successfully fabricated by coupling 2D g-C3N4 and 2D BiVO4 ultrathin nanosheets via a thermal-polymerization and subsequent hydrothermal method. The mass ratio between g-C3N4 and BiVO4 was optimized to improve the visible-light photocatalytic performance of CO2 reduction. Significantly, g-C3N4/BiVO4 (5:5) composite exhibited the optimal CO2 conversion efficiency towards CH4 (4.57 μmol g−1 h−1) and CO (5.19 μmol g−1 h−1), which were 4.8 and 4.4 folds higher than that of g-C3N4. The suitable band structures of single components induced the formed direct Z-scheme heterojunction, which efficiently suppressed the photoinduced carrier recombination and remained the strong redox capability. Moreover, the tight face-to-face interfacial contact between 2D g-C3N4 and 2D BiVO4 increased the transmission channels and accessible area for charges, and thereby facilitated charge transfer and provided abundant active sites for the photocatalytic reaction. Based on the trapping experiments, the photocatalytic mechanisms of g-C3N4/BiVO4 were reasonably proposed and validated by the photoluminescence spectra associated with time-resolved fluorescence decay. Furthermore, the repetitive photocatalytic experiments demonstrated the advantage of recyclability, which endowed 2D/2D Z-scheme g-C3N4/BiVO4 heterojunctions a promising application prospect.