Atomic-scale surface restructuring of copper electrodes under CO2 electroreduction conditions

Abstract

Potentiodynamic methods that induce structural changes in Cu catalysts for the electrochemical reduction of CO2 (CO2RR) have been identified as a promising strategy for steering the catalyst selectivity towards the generation of multi-carbon products. In current approaches, active species are created via a sequential Cu oxidation–reduction process. Here we show by in situ scanning tunnelling microscopy, surface X-ray diffraction and Raman spectroscopy measurements that low-coordinated Cu surface species form spontaneously near the onset of CO2 electrocatalytic reduction. This process starts by CO-induced Cu nanocluster formation in the initial stages of the reaction, leading to irreversible surface restructuring that persists over a wide potential range. On subsequent potential increase, the nanoclusters disperse into Cu adatoms, which stabilize reaction intermediates on the surface. The observed self-induced formation of undercoordinated sites on the CO2-converting Cu catalyst surface can account for its reactivity and may be exploited to (re)generate active CO2RR sites by potentiodynamic protocols. [Figure not available: see fulltext.].