Atypical Oxygen-bearing Copper Boosts Ethylene Selectivity toward Electrocatalytic CO2 Reduction.

Oxygen-bearing copper (OBC) has been widely studied for enabling the C-C coupling of the electrocatalytic CO2 reduction reac-tion (CO2RR) since this is a distinctive hallmark of strongly correlated OBC systems and may benefit many other Cu-based cata-lytic processes. Unresolved problems, however, include the instability of, and limited knowledge regarding, OBC under realistic operating conditions, raising doubts about its role in CO2RR. Here, an atypical and stable OBC catalyst with a hierarchical pore and nanograin-boundary structure was constructed and was found to exhibit efficient CO2RR for production of ethylene with a Faradaic efficiency of 45 percent at a partial current density of 44.7 mA cm-2 in neutral media, and the ethylene partial current density is nearly 26 and 116 times as that of oxygen-free copper (OFC) and commercial Cu foam, respectively. More importantly, the structure-activity relationship in CO2RR was explored through a comprehensive analysis of experimental data and computa-tional techniques, thus increasing the fundamental understanding of CO2RR. A systematic characterization analysis suggests that atypical OBC (Cu4O) was formed and that it is stable even at -1.00 V [(vs. reversible hydrogen electrode (RHE)]. Density func-tional theory calculations show that the atypical OBC enables control over CO adsorption and dimerization, making it possible to implement a preference for the electrosynthesis of ethylene (C2) products. These results provide insight into the synthesis and structural characteristics of OBC, as well as its interplay with ethylene selectivity.