Anchoring Cs⁺ Ions on Carbon Vacancies for Selective CO₂ Electroreduction to CO at High Current Densities in Membrane...

Electrolyte cations have been demonstrated to effectively enhance the rate and selectivity of the electrochemical CO₂ reduction reaction (CO₂RR), yet their implementation in electrolyte-free membrane electrode assembly (MEA) electrolyzer presents significant challenges. Herein, an anchored cation strategy that immobilizes Cs⁺ on carbon vacancies was designed and innovatively implemented in MEA electrolyzer, enabling highly efficient CO₂ electroreduction over commercial silver catalyst. Our approach achieves a CO partial current density of approximately 500 mA cm^-2 in the MEA electrolyzer, three-fold enhancement compared to pure Ag. In situ Raman and theoretical analyses, combined with machine learning potentials, reveal anchored Cs induces an electric field that significantly promotes the adsorption of *CO₂ ^- intermediates through performing muti-point energy calculations on each structure. Furthermore, reduced adsorption of *OH intermediates effectively hampers competing hydrogen evolution reaction, as clarified by disk electrode experiments and density functional theory studies. Additionally, coupling our system with commercial polysilicon solar cells yields a notable solar-to-CO energy conversion efficiency of 8.3 %. This study opens a new avenue for developing effective cation-promoting strategy in MEA reactors for efficient CO₂RR.