Salt Precipitation in Zero‐Gap CO 2 Membrane Electrode Assemblies: Strategies for Long‐Term Operation

Membrane electrode assembly (MEA)‐based CO 2 electrolyzers enable high‐rate electrochemical CO 2 reduction reaction (CO 2 RR) with industrially relevant current densities, but their durability is often limited by salt precipitation and electrode flooding. This review aims to elucidate the mechanisms of salt formation in zero‐gap MEA systems, emphasizing the coupled roles of ionic transport, water flux, and carbonate chemistry. Recent advances in mitigating salt precipitation are summarized through (i) system‐component engineering, including hydrophobic electrode design, electrolyte optimization, flow‐field modification, and membrane permselectivity control, and (ii) operational strategies such as elevating temperature, periodic flushing, and pulsed electrolysis. Furthermore, the emerging potential of acidic MEA systems that suppress carbonate crossovers is highlighted while discussing their concurrent challenges in water management. Finally, future directions toward integrated material–system–operation codesign are outlined to achieve stable, scalable, and CO 2 ‐efficient electrolyzer. This work provides a framework for understanding and controlling salt precipitation, guiding the development of next‐generation MEA‐based CO 2 electroreduction technologies.