Electrolytic CO2 reduction in membrane electrode assembly: Challenges in (Bi)carbonate, crossover, and stability

Abstract

Membrane electrode assembly (MEA) electrolyzers for carbon dioxide reduction reaction (CO₂RR) present a transformative approach for reducing CO₂ emissions while producing valuable chemicals. However, their commercialization is still hindered by several inherent challenges. This review outlines these critical bottlenecks and highlights recent advances aimed at enhancing the performance of CO₂R MEA electrolyzers. First, the in-situ generated carbonate and bicarbonate species at the cathode can migrate to the anode or form salt precipitates, which reduces carbon efficiency (CO₂-to-products) and obstructs gas diffusion channels. Second, product crossover can be diluted or even re-oxidized at the anode, resulting in increased energy consumption for product separation and electrolyte regeneration. Finally, the stability of CO₂R MEA electrolyzers, particularly when producing multi-carbon (C₂₊) products, remains far insufficient for commercial viability, as degradation of the catalyst layer, gas diffusion electrode, and anolyte significantly impacts performance. To address these challenges, this review identifies potential solutions and future directions, including pure-water-fed strategy, hydrophobic catalyst layer designs, and membrane customization.