Long-term stable acidic electroreduction of CO₂ to C₂ products at industrial current density using passivated copper

Acidic CO₂ electroreduction to multi-carbon (C₂₊) products using Cu-based catalyst has attracted considerable attention for CO₂ recycling due to high single-pass CO₂ utilization. However, its development is drastically limited by the poor stability, especially at high current density, caused by Cu dissolution/reconstruction during the reaction. Herein, we find the trace dissolved oxygen in the electrolyte accounts for the Cu dissolution/reconstruction and report an in-situ passivation strategy to prevent oxygen adsorption for inhibiting Cu dissolution/reconstruction for high stability CO₂-to-C₂₊ conversion. Theoretical and in situ spectroscopy demonstrate that aluminum citrate (AC) passivation layer decreases the adsorption of oxygen on Cu surface to effectively prevent the Cu oxidation, which is beneficial for the formation and adsorption of linearly bonded *CO toward C-C coupling. As the result, the Cu catalysts with AC layer achieve over 60% Faradaic efficiency C₂H₄ and 38.7% energy efficiency to C₂₊ for over 150 h stability at 500 mA cm^-2 in strong acidic electrolyte.