Increasing CO Binding Energy and Defects by Preserving Cu Oxidation State via O<sub>2</sub>-Plasma-Assisted N Doping on CuO Enables High C<sub>2+</sub> Selectivity and Long-Term Stability in Electrochemical CO<sub>2</sub> Reduction
Dong Gyu Park, Jae Won Choi, Hoje Chun, Hae Sung Jang, Heebin Lee, Won Ho Choi, Byeong Cheul Moon, Keon‐Han Kim, Min Gyu Kim, Kyung Min Choi, Byungchan Han, Jeung Ku Kang
Abstract
Cu is considered as the most promising catalyst for the electrochemical carbon dioxide reduction reaction (CO 2 RR) to produce C 2+ hydrocarbons, but achieving high C 2+ product selectivity and efficiency with long-term stability remains one of great challenges. Herein, we report a strategy to realize the CO 2 RR catalyst allowing high C 2+ product selectivity and stable catalytic properties by utilizing the benefits of oxygen-plasma-assisted nitrogen doping on CuO. It is exhibited that the defects such as oxygen vacancies and grain boundaries suitable for CO 2 RR are generated by N 2 plasma radicals on CuO. Also, the oxidation state of Cu is maintained without Cu reduction by O 2 plasma. Indeed, ON–CuO synthesized through oxygen-plasma-assisted nitrogen doping is demonstrated to enable a high C 2+ product selectivity of 77% (including a high C 2 H 4 selectivity of 56%) 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 22 h without performance degradation. High CO 2 RR performances are ascribed to the increased CO binding energy and catalytic sites in N-doped CuO. Furthermore, an in situ X-ray absorption near-edge structure analysis reveals that the defects in ON–CuO are favorable for C–C coupling leading to C 2+ products.