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

Abstract

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-CuNx 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 CuNx on Ag surface, i.e., Ag@Cu-CuNx. 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-CuNx electrocatalyst. This work provides a new approach to design Cu-based electrocatalysts with high-efficiency, mild condition, and stable CO2RR to C2 products.