Steering Electrochemical\nCO<sub>2</sub> Reduction\nSelectivity toward CH<sub>4</sub> or C<sub>2</sub>H<sub>4</sub> on\nN‑Doped Carbon-Coated Cu/Cu<sub>2</sub>O Composite Catalysts

Understanding the catalytic mechanism is crucial for\nthe rational\ndesign of efficient catalysts. However, the dynamic reconstruction\nof copper (Cu) catalysts under harsh electrochemical CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) conditions poses great challenges\nfor studying the mechanism. Herein, we prepared a series of N-doped\ncarbon-coated Cu/Cu<sub>2</sub>O composite catalysts with varying\nCu/Cu<sub>2</sub>O ratios and N-doping levels by annealing copper\nacetylacetonate (Cu(acac)<sub>2</sub>) with different amounts of potassium\nnitrate (KNO<sub>3</sub>), which can steer CO<sub>2</sub>RR toward\neither CH<sub>4</sub> or C<sub>2+</sub> (mainly C<sub>2</sub>H<sub>4</sub>) production. The <i>in situ</i> formed carbon layer\neffectively stabilized the Cu catalyst structures under cathode potentials,\nfacilitating mechanistic studies of CO<sub>2</sub>RR. Through CO temperature-programmed\ndesorption (TPD) and <i>in situ</i> infrared spectroscopy\ncharacterizations, it is revealed that the coexistence of Cu<sup>0</sup> and Cu<sup>+</sup> sites promoted the generation of a high-coverage,\nstrongly adsorbed *CO intermediate on the catalytic surface, thereby\nenhancing C–C coupling to generate C<sub>2+</sub> products.\nConversely, the surface with only Cu<sup>0</sup> sites exhibited a\nlow-coverage and weakly adsorbed *CO, benefiting its hydrogenation/deoxygenation\ntoward CH<sub>4</sub> production.