Constructing and stabilizing Cu/Cu sites through dual chlorine-induced strategy for CO electroreduction to CH.

Cu-based catalysts with Cu/Cu dual sites demonstrate unique synergistic advantages in promoting CO electroreduction. To construct effective Cu/Cu sites, inhibiting over-reduction of Cu species is essential while remains a critical challenge due to their inherent thermodynamic instability. Herein, we propose a dual chlorine regulation strategy involving chlorine doping within the CuO matrix and chlorine supplementation in the electrolyte to enhance the stability and activity of Cu/Cu sites during CO-to-CH conversion. Notably, the chlorine-doped CuO (Cl-CuO) electrode in 0.1 M KHCO + 0.2 M KCl exhibited a ∼2.5-fold improvement in ethylene Faradaic efficiency (FE increased from 13.0 % to 32.0 %) along with a 4-fold enhancement in operational lifetime compared to pristine CuO evaluated in 0.3 M KHCO. The combined results of control experiments, theoretical calculations and in situ characterizations demonstrate that the strong electronic interaction between Cu and Cl effectively suppressed oxygen vacancy formation and retarded the reduction kinetics of Cu species in reconstructed Cu/Cu active sites, which further lowered the energy barrier for adsorption of *CO intermediates and facilitated the C-C coupling. Furthermore, introducing Cl into the electrolyte significantly mitigated chlorine leaching from the catalyst surface, making Cu/Cu active sites stably operate for CH production. This study provided a novel insight into the stability enhancement mechanism of Cu/Cu sites and offered a reference for design of Cu-based catalysts for more electrocatalytic reactions.