Stabilizing local electric fields via porous membranes in AgCu bilayer electrodes for CO2-to-ethylene conversion

Cu-based catalysts are known to undergo phase transformation into Cu(OH)2 during the electrochemical CO2 reduction reaction (CO2RR), leading to Cu dissolution and limiting long-term operational stability. To address this challenge, a double-layered Ag–CuO electrode was engineered, wherein the Ag buffer layer facilitates local CO generation and enables the redeposition of dissolved Cu, forming dendritic Cu structures that promote C–C coupling. The optimized electrode with an Ag:CuO ratio of 7:3 exhibited a maximum Faradaic efficiency for ethylene of ~50% and a partial current density of 295 mA cm⁻2. However, the growth of dendritic Cu induced local electric field intensification, resulting in mechanical degradation of the anion exchange membrane (AEM). To overcome this issue, a porous membrane was introduced, effectively suppressing membrane failure and extending operational stability beyond 30 hours at 200 mA cm⁻2, while maintaining an ethylene Faradaic efficiency above 46%. This work demonstrates a practical strategy for simultaneously enhancing catalytic performance and membrane durability in zero-gap CO2 electrolyzer systems, offering a viable pathway toward scalable CO2 conversion technologies.