Copper–Gold Interactions Enhancing Formate Production from Electrochemical CO2 Reduction

Strong interactions between two different types of metal nanoparticles can dramatically change their electrocatalytic properties but are underexplored. Herein we show that interactions with Au can turn Cu, which by itself is neither selective nor active for electrochemical CO2 reduction to formate, into a much improved electrocatalyst for the same reaction. Our Cu/Au catalyst produces formate in a significant yield at −0.4 V vs the reversible hydrogen electrode in a near-neutral electrolyte and achieves a partial current density of 10.4 mA cm–2 and a Faradaic efficiency of 81% at −0.6 V, which is 15 times more active and 4 times more selective than the control Cu catalyst derived in the same way but without Au. Electrochemical and spectroscopic studies reveal that the metal–metal interactions in the Cu/Au catalyst lead to the disappearance of Au's characteristic electrocatalytic activity for reducing CO2 and for oxidizing CO and to the stabilization of Cu1+ species on the Cu surface at CO2 reduction potentials. Enhanced formate production from CO2 electroreduction is now unlocked for the Cu–Au bimetallic system, implicating vast possibilities to improve electrocatalytic reactivity utilizing metal–metal interactions.