Morphological and chemical state effects in pulsed CO₂ electroreduction on Cu(100) unveiled by correlated spectro-microscopy

Subjecting copper to short anodic pulses during the electrocatalytic reduction of carbon dioxide (CO₂ RR) has been shown to improve the activity and selectivity towards hydrocarbons and alcohols. Nonetheless, the nature of the active sites is still unclear. Here the evolution of the morphology, chemical state and crystal structure of Cu(100) exposed to potential pulses during the CO₂RR was resolved by a combination of spectroscopy, microscopy and diffraction methods applied concurrently. Under anodic potential pulses, (n10) facets were formed. Moreover, alternating anodic to cathodic potential pulses during the CO₂RR also lead to the stabilization of copper oxide species located either at the surface or directly underneath ultrathin metallic copper layers, depending on the specific pulse potential treatment applied. Both findings are key for the enhanced ethylene and ethanol production reported during pulsed CO₂RR.