Bifunctional S-scheme g-C3N4/Bi/BiVO4 hybrid photocatalysts toward artificial carbon cycling

Abstract

Although both the aerobic photocatalytic oxidation of organic pollutants into CO2 and the anaerobic photocatalytic reduction of CO2 into solar fuels have been intensively studied, few efforts have been devoted to combining these carbon-involved photocatalytic oxidation-reduction processes together, by which an artificial photocatalytic carbon cycling process can be established. The key challenge lies in the exploitation of efficient bifunctional photocatalysts, capable of triggering both aerobic oxidation and anaerobic reduction reactions. In this work, a bifunctional ternary g-C3N4/Bi/BiVO4 hybrid photocatalyst is successfully constructed, which not only demonstrates superior aerobic photocatalytic oxidation performance in degrading an organic pollutant (using the dye, Rhodamine B as a model), but also exhibits impressive photocatalytic CO2 reduction performance under anaerobic conditions. Moreover, a direct conversion of Rhodamine B to solar fuels in a one-pot anaerobic reactor can be achieved with the as-prepared ternary g-C3N4/Bi/BiVO4 hybrid photocatalyst. The excellent bifunctional photocatalytic performance of the g-C3N4/Bi/BiVO4 photocatalyst is associated with the formation of efficient S-scheme hybrid junctions, which contribute to promoting the appropriate charge dynamics, and sustaining favorable charge potentials. The formation of the S-scheme heterojunction is supported by scavenger studies and density functional theory calculations. Moreover, the in-situ formed plasmonic metallic Bi nanoparticles in the S-scheme hybrid g-C3N4/Bi/BiVO4 photocatalyst enhances vectorial interfacial electron transfer. This novel bifunctional S-scheme g-C3N4/Bi/BiVO4 hybrid photocatalyst system provides new insights for the further development of an integrated aerobic-anaerobic reaction system for photocatalytic carbon cycling.