Steering Electrochemical CO<sub>2</sub> Reduction Selectivity toward CH<sub>4</sub> or C<sub>2</sub>H<sub>4</sub> on N-Doped Carbon-Coated Cu/Cu<sub>2</sub>O Composite Catalysts
Feifei Li, Hossain Tariq, Huaqian Yang, Yuyang Cao, Zhou Tang, Gongwei Wang
Abstract
Understanding the catalytic mechanism is crucial for the rational design of efficient catalysts. However, the dynamic reconstruction of copper (Cu) catalysts under harsh electrochemical CO 2 reduction reaction (CO 2 RR) conditions poses great challenges for studying the mechanism. Herein, we prepared a series of N-doped carbon-coated Cu/Cu 2 O composite catalysts with varying Cu/Cu 2 O ratios and N-doping levels by annealing copper acetylacetonate (Cu(acac) 2 ) with different amounts of potassium nitrate (KNO 3 ), which can steer CO 2 RR toward either CH 4 or C 2+ (mainly C 2 H 4 ) production. The in situ formed carbon layer effectively stabilized the Cu catalyst structures under cathode potentials, facilitating mechanistic studies of CO 2 RR. Through CO temperature-programmed desorption (TPD) and in situ infrared spectroscopy characterizations, it is revealed that the coexistence of Cu 0 and Cu + sites promoted the generation of a high-coverage, strongly adsorbed *CO intermediate on the catalytic surface, thereby enhancing C–C coupling to generate C 2+ products. Conversely, the surface with only Cu 0 sites exhibited a low-coverage and weakly adsorbed *CO, benefiting its hydrogenation/deoxygenation toward CH 4 production.