Hierarchical Ag-Cu interfaces promote C-C coupling in tandem CO2 electroreduction

Electrocatalytic CO2 reduction into ethanol driven by renewable energy represents a promising strategy for energy storage and mitigation of global warming, but it has remained challenging to gain high activity and selectivity of ethanol. Here we take advantage of atomic arrangement in immiscible Ag-Cu composite during annealing and establish hierarchical interfaces in the obtained core-shell catalyst. The atomic Ag-Cu interactions increase electrochemical surface area and expedite charge dynamics, resulting in an unprecedented electrocatalytic performance with the faradaic efficiency of C2+ products, ethanol as 80.2 %, 52.6 % and the current density of ∼320 mA cm−2 at −1.0 V (versus reversible hydrogen electrode). Moreover, the Ag-Cu catalyst exhibits a notable stability for ∼60 h. Mechanism studies reveal that local CO intermediates preferentially accumulate on the core, then migrate to the continuous Cu surface for C-C coupling energy-favorably toward ethanol. Our work highlights a novel design principle as interface engineering for advanced tandem electrocatalysts.