Increasing CO Binding Energy and Defects by Preserving Cu Oxidation State via O-2-Plasma-Assisted N Doping on CuO Enables High C2+ Selectivity and Long-Term Stability in Electrochemical CO2 Reduction

Abstract

Cu is considered as the most promising catalyst for theelectrochemicalcarbon dioxide reduction reaction (CO2RR) to produce C2+ hydrocarbons, but achieving high C2+ productselectivity and efficiency with long-term stability remains one ofgreat challenges. Herein, we report a strategy to realize the CO2RR catalyst allowing high C2+ product selectivityand stable catalytic properties by utilizing the benefits of oxygen-plasma-assistednitrogen doping on CuO. It is exhibited that the defects such as oxygenvacancies and grain boundaries suitable for CO2RR are generatedby N-2 plasma radicals on CuO. Also, the oxidation stateof Cu is maintained without Cu reduction by O-2 plasma.Indeed, ON-CuO synthesized through oxygen-plasma-assisted nitrogendoping is demonstrated to enable a high C2+ product selectivityof 77% (including a high C2H4 selectivity of56%) with a high current density of -34.6 mA/cm(2) at -1.1 V vs RHE, as well as a long-term stability for 22h without performance degradation. High CO2RR performancesare ascribed to the increased CO binding energy and catalytic sitesin N-doped CuO. Furthermore, an in situ X-ray absorption near-edgestructure analysis reveals that the defects in ON-CuO are favorablefor C-C coupling leading to C2+ products.