Cu-C(O) Interfaces Deliver Remarkable Selectivity and Stability for CO2 Reduction to C2+ Products at Industrial Current Density of 500 mA cm-2

The electrocatalytic CO2 reduction reaction (CO2RR) is an attractive technology for CO2 valorization and high-density electrical energy storage. Achieving a high selectivity to C2+ products, especially ethylene, during CO2RR at high current densities (>500 mA cm(-2)) is a prized goal of current research, though remains technically very challenging. Herein, it is demonstrated that the surface and interfacial structures of Cu catalysts, and the solid-gas-liquid interfaces on gas-diffusion electrode (GDE) in CO2 reduction flow cells can be modulated to allow efficient CO2RR to C2+ products. This approach uses the in situ electrochemical reduction of a CuO nanosheet/graphene oxide dots (CuO-C(O)) hybrid. Owing to abundant Cu-O-C interfaces in the CuO-C(O) hybrid, the CuO nanosheets are topologically and selectively transformed into metallic Cu nanosheets exposing Cu(100) facets, Cu(110) facets, Cu[n(100) x (110)] step sites, and Cu+/Cu-0 interfaces during the electroreduction step, -the faradaic efficiencie (FE) to C2+ hydrocarbons was reached as high as 77.4% (FEethylene approximate to 60%) at 500 mA cm(-2) . In situ infrared spectroscopy and DFT simulations demonstrate that abundant Cu+ species and Cu-0/Cu+ interfaces in the reduced CuO-C(O) catalyst improve the adsorption and surface coverage of *CO on the Cu catalyst, thus facilitating C-C coupling reactions.

Automated summary

Efficient electrocatalytic CO2 reduction to C2+ products can be achieved by modulating the surface and interfacial structures of Cu catalysts and the solid-gas-liquid interfaces on gas-diffusion electrodes in CO2 reduction flow cells. In this study, a CuO nanosheet/graphene oxide dots hybrid was used for in situ electrochemical reduction, leading to high selectivity (up to 77.4% for C2+ hydrocarbons) with the presence of abundant Cu+ species and Cu-0/Cu+ interfaces. The improved adsorption and surface coverage of *CO on the Cu catalyst facilitated C-C coupling reactions.