Highly dispersive trace silver decorated Cu/Cu2O composites boosting electrochemical CO2 reduction to ethanol

Abstract Selective CO2 electroreduction to C2+ products, especially ethanol, is regarded as a potential technology for CO2 utilization but is still a formidable challenge. Herein, we report the highly dispersive trace Ag decorated copper/copper oxide composite (Cu/Cu2O-Ag-x) for efficient electrochemical CO2 reduction to C2+ products, mainly containing ethylene and ethanol. Physical measurements confirm that the Ag decoration is an effective strategy to tune the surface electronic structure but without changing the valence and morphology of Cu. The performance evaluation of electrochemical CO2 reduction in a flow cell demonstrates that the activity and selectivity for ethanol production on Cu/Cu2O can be promoted by the trace Ag modification. The best catalyst, Cu/Cu2O with merely 0.6 at.% silver decoration, exhibits a significant enhancement in C2+ selectivity (60.9 %) as compared to the Ag-free Cu/Cu2O catalyst (50.4 %). Originated from the formed Cu-Ag sites and thus enhanced affinity with oxygen-adsorbed intermediates on Cu/Cu2O-Ag-x catalysts, the ethanol formation is favored with a greatly improved Faradaic efficiency (19.2 %) as well as partial current density (305 mA cm−2), which are superior to those of Ag-free counterpart (9.1 %, 105 mA cm−2). Moreover, the products selectivity remains stable even electrolysis at 900 mA cm−2 over 8 h, demonstrating the preeminent electrocatalytic stability.