Au nanoparticles-modified S-scheme In2O3/H1.5CN heterojunction with enhanced photocatalytic CO2 reduction activity

The construction of S-scheme heterojunction is of great significance for the photocatalytic reduction of CO2. Here, we prepared two-dimensional (2D) ultra-thin g-C3N4 by acidifying the carbon nitride precursor, and used In2O3 to construct a S-scheme heterojunction with 2D g-C3N4, and finally In2O3/H1.5CN was modified with Au nanoparticles. The physicochemical properties of the prepared materials were studied by SEM/TEM, XPS, DRS, PL and photochemical test. Meantime, the S-scheme charge transfer mechanism was demonstrated by UPS and ESR. As a result, on the one hand, S-scheme heterojunction accelerated the transfer of electrons on the CB of In2O3 to the VB of g-C3N4, avoided the recombination of photon-generated carrier. On the other hand, Au, as an effective cocatalyst, promoted photoinduced electron transfer and provided more active sites for CO2 reduction and the local surface plasmon resonance phenomenon caused by Au NPs enhanced the visible light absorption capacity of the composite material. Moreover, 2D thin layer of g-C3N4 played a carrier effect to disperse In2O3 cube. Therefore, In2O3/H1.5CN/2Au had stable CO2 reduction products, and the yields of CO/CH4 reached 141.24/77.05 μmol/g.