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

Cu-based catalysts are known to undergo phase transformation into Cu(OH) 2 during the electrochemical CO 2 reduction reaction (CO 2 RR), 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 h 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 CO 2 electrolyzer systems, offering a viable pathway toward scalable CO 2 conversion technologies. • Double-layered Ag-CuO electrodes enhanced CO 2 RR via Cu redeposition on Ag buffer layer. • Optimized 7:3 (Ag:CuO) electrode achieved ∼50 % ethylene FE at 600 mA cm −2 . • Cu dendrites induced local electric fields, degrading the anion exchange membrane • Porous membrane suppressed failure, maintaining >46 % ethylene FE for 32 h at 200 mA cm −2 .