Membranes for Electrochemical Carbon Dioxide Conversion to Multi-Carbon Products

Electrochemical carbon dioxide reduction reaction (CO2RR) offers a promising route to mitigate climate change while simultaneously enabling renewable energy storage and the sustainable production of value-added chemicals. A wide variety of CO2RR reactor designs have been developed, including both liquid-phase cells and gas-phase configurations. Among these, gas-phase systems, particularly flow-cell and membrane electrode assembly (MEA) designs, have become the primary focus of recent research due to their ability to overcome mass transport limitations and operate at high currents. While catalyst development has received considerable attention in advancing CO2RR performance, the role of membranes in these gas-phase electrolyzers has been less systematically reviewed. This article addresses that gap by critically examining the functions, advantages, and limitations of the major membrane classes used in CO2 electrolysis: anion exchange membranes, cation exchange membranes, bipolar membranes, and non-ion-exchange porous membranes within flow-cell and MEA configurations. We highlight how membrane properties influence local pH regulation, water management, crossover behavior, and overall reactor performance, while emphasizing that product identity is primarily catalyst-determined. By analyzing recent progress and remaining challenges, this review provides design insights for membrane selection and development toward efficient, stable, and scalable CO2 electrolysis systems.