Hexafluorophosphate‐Modulated CuO for Selectivity Enhancement of C ₂ Species in Electroreduction of CO ₂

ABSTRACT Copper (Cu)‐based catalysts are widely employed in electroreduction of carbon dioxide (CO 2 ER) because of their cost‐effectiveness and versatility in producing multi‐carbon products. However, improving the product selectivity, especially toward C 2 species (hydrocarbon containing two carbon atoms), remains a significant challenge. Herein, the microwave‐assisted synthesis of copper oxide (CuO) is modulated with ammonium hexafluorophosphate (NH 4 PF 6 ), obtaining thin CuO (ca. 12 nm in thickness) nanosheets with the surface adsorbed with hexafluorophosphate, referred as CuO‐PF 6 . This CuO‐PF 6 catalyst could help stabilize the key reaction intermediates during CO 2 ER. Therefore, the Faradaic efficiency (FE) of C 2 products (ethylene and ethanol) during CO 2 ER could be improved to 75.8% ± 0.5% in an H‐type electrochemical cell. This C 2 FE increases to 82.4% in a flow cell. The improved FE toward C 2 species could be attributed to the PF 6 ‐modulated electronic structure of Cu surface and stabilization of key reaction intermediates, especially those involving C 2 production. In addition, CuO‐PF 6 also demonstrates a high catalytic stability over 10 h. This work provides a deeper understanding of surface modification strategy for CO 2 ER enhancement, promising for designing hybrid electrocatalysts with high efficiency and stability for CO 2 ‐to‐fuel conversion.