Boosting the Electroreduction of CO2 to Ethanol via the Synergistic Effect of Cu–Ag Bimetallic Catalysts

Electroreduction of CO2 to ethanol remains a formidable challenge due to the unsatisfactory efficiency of the C–C coupling process and the demand for complex oxygen-containing intermediates, thus resulting in poor selectivity and electrocatalytic activity. Cu–Ag bimetallic materials with adjustable electronic structures and active site exposure are promising catalysts to electrochemically convert CO2 to ethanol. Herein, we report Ag-decorated Cu2O materials to promote the catalytic performance of CO2 electroreduction to ethanol. The as-prepared CuAg-0.75% catalyst exhibited an improved ethanol Faradaic efficiency of 21.0% at −0.71 V (vs reversible hydrogen electrode (RHE)) and a maximum ethanol partial current density of 214.4 mA cm–2 at −0.74 V (vs RHE), which were ca. 2 times those of the counterpart without Ag decoration. Density functional theory (DFT) calculations revealed that the adsorption intensity of CO on Ag-decorated Cu surface was stronger than that on Ag surface; hence, the *CO spillover from Ag sites to Cu sites could be promoted, leading to a higher *CO coverage than that on pure Cu surface to facilitate the C–C coupling process. The evenly distributed Ag atoms provided abundant Ag sites for CO formation and a short CO transfer distance. Furthermore, the free energy of formation of key intermediates toward ethanol pathway was lower on the Ag-doped sample, which led to enhanced ethanol selectivity. Both the improved CO spillover process and the optimization of free energy on the Ag-decorated sample resulted in a better catalytic performance toward ethanol.