Ternary heterojunction in rGO-coated Ag/Cu2O catalysts for boosting selective photocatalytic CO2 reduction into CH4

Herein, the ternary catalyst of reduced graphene oxide (rGO)-coated Ag/Cu2O-octahedron nanocrystals (Ag/Cu2O@rGO) was successfully fabricated by method of water bath combining with gas-bubbling-assisted membrane reduction. Supported Ag nanoparticles with low fermi energy can enrich the photogenerated electrons originated from visible light-driven Cu2O octahedral nanocrystals. The surface extended π bond of coated rGO nanolayers on Ag/Cu2O can further capture photoelectrons and improve adsorption-activation capacities for reactants. Agn/Cu2O@rGO catalysts with ternary rGO-Ag-Cu2O heterojunction exhibit excellent performance during selective photocatalytic CO2 reduction with H2O into CH4. Ag4/Cu2O@rGO catalyst has the highest formation rate (82.6 μmol g−1 h−1) and selectivity (95.4%) of CH4 product. Combined with the results of in-situ DRIFT spectra and density functional theory calculations, the photocatalytic mechanism is proposed: the protonation of CO* intermediate is key step for selective photocatalytic CO2 reduction into CH4. It provides one novel strategy to development of high-efficient photocatalyst for selective CO2 conversion into C1 chemicals. [Display omitted] •Novel rGO-coated Ag/Cu2O-octahedron photocatalysts were designed and fabricated.•Supported Ag NPs enrich the photoelectrons originated from visible light-driven Cu2O.•Surface π bond of coated rGO nanolayers improve adsorption-activation capacities for CO2.•Ag/Cu2O@rGO catalysts exhibit high performances for selective CO2 reduction into CH4.•Protonation of CO* intermediate is key step for photocatalytic CO2 reduction into CH4.