Stabilizing local electric fields via porous membranes in Ag[sbnd]Cu 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[sbnd]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 CO₂ electrolyzer systems, offering a viable pathway toward scalable CO₂ conversion technologies.