Beyond Faradaic Efficiency: Towards efficient electroreduction of CO2 in Membrane-Electrode assemblies

Electrochemical CO 2 reduction reaction (CO 2 RR) offers a promising route to convert CO 2 into valuable fuels and chemicals, particularly valuable multi-carbon products using renewable energy sources. While significant advances have been achieved using flow cells taking advantage of the triple phase: gas/liquid/solid interface, membrane-electrode assembly (MEA) electrolyzers are considered as the most scalable and industrially relevant architecture. However, the unique solid–gas interface and absence of a bulk liquid electrolyte in MEA systems introduce a complex and poorly understood microenvironment that critically influences performance and selectivity. This review provides a comprehensive analysis of recent strategies to enhance CO 2 RR efficiency and stability in MEA electrolyzers. We dissect the design principles and advancements in key MEA components—including cathode catalysts, ion-exchange membranes, and anodes—as well as innovations in flow field engineering. Particular emphasis is placed on approaches to modulate the local reaction environment at the cathode, such as molecular or ionomer functionalization, hierarchical structuring, and tandem catalysis at the atomic scale. We also assess the roles of membrane selection and anodic coupling reactions in improving carbon utilization. We further systematically discuss the core challenges and integrative optimization strategies for MEA scale-up. The scale-up of MEA electrolyzers is proven to be a multi-physics coupled problem involving mechanical compression, mass transport, and thermal dynamics, rather than simple geometric enlargement. We analyze the performance degradation mechanisms of single-cell area expansion and multi-cell stacking, and highlight feasible scalable pathways including segmented flow field design, thermally and hydraulically balanced stack configuration, and precise water/thermal management. Combined with the matching of industrial CO 2 feedstocks and renewable power inputs, we elucidate viable technical routes for the practical deployment of large-scale CO 2 RR systems. Finally, this review concludes the current technical bottlenecks and provides a prospective roadmap for the future development and commercialization of MEA-based CO 2 electrolysis technology.