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

The electrocatalytic CO 2 reduction reaction (CO 2 RR) is an attractive technology for CO 2 valorization and high-density electrical energy storage. Achieving a high selectivity to C 2+ products, especially ethylene, during CO 2 RR 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 CO 2 reduction flow cells can be modulated to allow efficient CO 2 RR to C 2+ 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) × (110)] step sites, and Cu + /Cu 0 interfaces during the electroreduction step, the faradaic efficiencie (FE) to C 2+ hydrocarbons was reached as high as 77.4% (FE ethylene  ≈ 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.