The role of in situ generated morphological motifs and Cu(i) species in C2+ product selectivity during CO2 pulsed electroreduction

Carbon dioxide can be reduced electrocatalytically to fuels using copper catalysts, but the key features that determine the selectivity of these materials to specific products remains uncertain. Here Aran-Ais et al. use in situ methods to explore the influence of morphology and oxidation state on the performance of copper catalysts. The efficient electrochemical conversion of CO2 provides a route to fuels and feedstocks. Copper catalysts are well-known to be selective to multicarbon products, although the role played by the surface architecture and the presence of oxides is not fully understood. Here we report improved efficiency towards ethanol by tuning the morphology and oxidation state of the copper catalysts through pulsed CO2 electrolysis. We establish a correlation between the enhanced production of C2+ products (76% ethylene, ethanol and n-propanol at -1.0 V versus the reversible hydrogen electrode) and the presence of (100) terraces, Cu2O and defects on Cu(100). We monitored the evolution of the catalyst morphology by analysis of cyclic voltammetry curves and ex situ atomic force microscopy data, whereas the chemical state of the surface was examined via quasi in situ X-ray photoelectron spectroscopy. We show that the continuous regeneration of defects and Cu(i) species synergistically favours C-C coupling pathways.