CO2 Electroreduction to Ethylene in MEA Electrolyzers: Multiscale Degradation Mechanisms and Stability Engineering

Electrochemical CO2 reduction to ethylene enables a carbon-neutral feedstock supply, yet its practical deployment is bottlenecked by the long-term durability and scalability of membrane electrode assemblies (MEAs). This review traces the evolution of electrolyzer architectures from H-cells to zero-gap MEAs and industrial stacks, as well as the fabrication of MEAs, highlighting the trade-offs among reaction kinetics, mass transport, and stability. We further analyze multiscale degradation mechanisms spanning from nanoscale catalyst reconstruction, ionomer deactivation, and substrate corrosion to macroscale flooding, salt precipitation, and delamination across catalyst layers, membrane interfaces, and local catalytic microenvironments. To address these challenges, corresponding mitigation strategies targeting catalysts, membranes, and devices are systematically evaluated, focusing on advanced structural designs including gradient-hydrophobic catalyst layers, 3D porous electrodes, and tailored flow fields, alongside dynamic operational modes (e.g., pulsed feeds, periodic flushing, and pressure/thermal tuning). Finally, actionable perspectives on scaling ethylene electrosynthesis to the kilogram level are outlined, encompassing flow-field engineering, superhydrophobic electrode design, downstream process integration, and machine-learning–driven lifetime prediction. Taken together, this review provides comprehensive insights into overcoming stability bottlenecks, mapping the path toward commercial ethylene electrosynthesis.