In-situ electrochemical interface of Cu@Ag/C towards the ethylene electrosynthesis with adequate *CO supply

The conversion of carbon dioxide to ethylene by electrochemical reduction (CO 2 RR) provides a new strategy for achieving carbon dioxide conversion. However, copper-based catalysts have the disadvantages of unsatisfactory selectivity and low current density, which limit the potential CO 2 RR industrial expansion. Researches have verified that the real reaction sites at the catalyst surface often undergo reconstruction during the reaction, therefore, understanding and utilizing this phenomenon is crucial for improving catalytic performance. In this work, we introduced additional Ag component into Cu@Ag/C tandem catalyst by in-situ electrochemical reconstruction of Cu 2 CO 3 (OH) 2 /AgCl/C precursor. This electro-reduced catalyst exhibits a C 2 H 4 Faradaic efficiency of 50.41% in H-cell, and 58.03% in the flow cell, surpassing the counterparts of pure Cu and Ag, as well as the Cu-Ag homolog with separated interface. Moreover, it also provides a long-term stability of 21 h with the ethylene Faraday efficiency (FE) over 50%. The appropriate amount of Ag dopant into the Cu catalyst changes the electronic structure of Cu surface by the electron transfer from Cu to Ag, which distinctly enhances the binding energy of CO 2 on the catalyst. Meanwhile, in-situ Raman results and theoretical calculation reveal that the introduction of silver increases the number of active sites and improves the coverage of *CO intermediate, thereby accelerating the kinetics of C–C coupling and reducing its energy barrier. The combination of cascade catalytic strategy and in-situ electroreduction interface provides potential applications for future artificial carbon balance.