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

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.