Phosphorus Coordination in Second Shell of Single-Atom Cu Catalyst toward Acetate Production in CO Electroreduction

It is challenging to achieve highly efficient CO-CO coupling toward C₂ products in electrochemical CO and CO₂ reductions on single-atom catalysts (SACs). Herein, we report a modulation strategy of phosphorus coordination in the second shell of Cu SACs with a Cu-N₄ structure (Cu-N₄-P₄/C₄) and demonstrate experimentally and theoretically the CO-CO coupling through an Eley-Rideal mechanism in electrochemical CO reduction (COR). Remarkably, the Cu SACs exhibit a selectivity of 63.9% toward acetate production in alkaline media on a gas diffusion electrode. Operando synchrotron-based X-ray absorption spectroscopy confirms the robust Cu-N₄-P₄/C₄ structure of the Cu SACs against the harsh electrochemical reduction conditions throughout the electrochemical COR, instead of forming Cu clusters for Cu-N₄ configuration, enabling an excellent COR performance toward acetate. This work not only unravels a new mechanism for CO-CO coupling toward C₂ products in COR but also offers a novel strategy for SAC regulation toward multicarbon production with high activity, selectivity, and durability.