Nitrogen cold plasma treatment stabilizes Cu⁰/Cu⁺ electrocatalysts to enhance CO₂ to C2 conversion

Cu-based materials are ideal catalysts for CO₂ electrocatalytic reduction reaction (CO₂RR) into multi-carbon products. However, such reactions require stringent conditions on local environments of catalyst surfaces, which currently are the global pressing challenges. Here, a stabilized activation of Cu⁰/Cu⁺-on-Ag interface by N₂ cold plasma treatment was developed for improving Faradaic efficiency (FE) of CO₂RR into C2 products. The resultant Ag@Cu-CuN_x exhibits a C2 FE of 72% with a partial current density of −14.9 mA cm⁻² at −1.0 V vs. RHE (reversible hydrogen electrode). Combining density functional theory (DFT) and experimental investigations, we unveiled that Cu⁰/Cu⁺ species can be controllably tuned by the incorporation of nitrogen to form CuN_x on Ag surface, i.e., Ag@Cu-CuN_x. This strategy enhances *CO intermediates generation and accelerates C–C coupling both thermodynamically and kinetically. The intermediates O*C*CO, *COOH, and *CO were detected by in-situ attenuated total internal reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The uncovered CO₂RR-into-C2 products were carried out along CO₂→ *COOH → *CO → O*C*CO → *C₂H₃O → *C₂H₄O → C₂H₅OH (or *C₂H₃O → *O + C₂H₄) paths over Ag@Cu-CuN_x electrocatalyst. This work provides a new approach to design Cu-based electrocatalysts with high-efficiency, mild condition, and stable CO₂RR to C2 products.