Constructing grain boundary to stabilize Cu⁰/Cu⁺ interfacial sites for efficient <scp>CO₂</scp> reduction reaction

Abstract The electrochemical CO 2 reduction reaction (CO 2 RR) to multi‐carbon (C 2+ ) products derived by renewable energy represents a promising strategy for mitigating CO 2 emissions. One of the intensively studied strategies is to stabilize Cu + species on catalysts to facilitate the adsorption of *CO intermediates. However, the reductive environment during CO 2 RR renders the Cu + species on the catalyst surface susceptible to reduction to Cu 0 . Here, we developed a GB‐Cu 2 O‐Cu catalyst featuring enriched grain boundaries via an in situ electrochemical reduction process to stabilize Cu + species, resulting in an abundance of Cu 0 /Cu + interfacial active sites. In situ x‐ray diffraction (XRD) and Raman spectroscopy further revealed that the presence of grain boundaries effectively shields the Cu + species on the catalyst surface from undergoing reduction during CO 2 RR, facilitating the concentration of *CO intermediates and thus promoting C‐C dimerization to C 2+ products.