Synergy Effect between Facet and Zero-Valent Copper for Selectivity Photocatalytic Methane Formation from CO2

The application of Cu2O catalysts in CO2photo-catalytic reduction has attracted much attention due to the capacityto generate high-calorific-value hydrocarbon fuels with pre-eminentselectivity. However, the origin of the high selectivity remainsunclear. In this study, the (111) facet of Cu2O was verified as theorigin of selectivity for CH4(the simplest hydrocarbon) formationby comparing the photocatalytic CO2reduction behaviors of Cu2Ocatalysts with varied active facets. Results showed that Cu2O-100produced negligible CH4(selectivity = 0%), whereas the yield ofCH4on Cu2O-111 was 12.24 mu molmiddotg-1middoth-1with a substantiallyhigh selectivity of 91.4%. After decoration with zero-valent copperon the surface of Cu2O-111 (Cu2O-111-Cu0), the yield of CH4reached 78.4 mu molmiddotg-1middoth-1,affording a selectivity of CH4as high as97%. In situ FT-IR and theoretical calculations showed that the(111) facet has stronger CO absorption capacity and electron reduction capacity for highly selective photocatalytic CO2conversion.Moreover, the presence of Cu0on the (111) facet could accelerate the carrier separation efficiency, thus providing more electrons forefficient hydrocarbon formation. This work provides a promising idea to design Cu2O catalysts for the conversion of CO2into highvalue-added hydrocarbon products with high activity and selectivity.