In situ synthesis of g-C3N4/Ag@Ag3PO4 S-scheme heterostructure with tandem ohmic- and d-p bond-junction for photocatalytic reduction of CO2

Abstract

Low-mass interfacial contacts and poor charge transfer efficiency severely limit the CO2 photoreduction performance of semiconductor heterojunctions. In this work, g-C3N4/Ag@Ag3PO4 S-scheme heterojunction is prepared by an in-situ growth method. The main product for CO2 photoreduction is CO with the selectivity of 97 %. The evolution rate of CO for optimal g-C3N4/Ag@Ag3PO4 heterojunction is 123.8 μmol g−1 h−1, which are 8.3-and 3.4-fold higher than those of pristine Ag3PO4 and g-C3N4, respectively. It is found that Ag3PO4, Ag, and g-C3N4 form strong interacting interfacial structure, in which Ag3PO4 links with Ag nanoparticles through tandem Ohmic contact. More importantly, σ bonds are formed via hybridization of px orbital for C and N with dx2-y2 orbitals of Ag in g-C3N4/Ag@Ag3PO4 S-scheme heterojunction, establishing an atomic-level dx2-y2(Ag)-px(C,N) charge flow highway. This work provides new viewpoints into the design of heterojunction photocatalysts with high-quality interfaces and highlights the insights of charge transfer behavior in regulating the catalytic activity.