Mitigation of gas-induced damage in bipolar membranes for CO₂ electrolysis

Bipolar membranes operated in forward bias are a promising platform for CO₂ electrolysis, enabling alkaline cathode environments and pure-water feed while preventing CO₂ crossover and salt precipitation. However, their deployment is limited by structural degradation under sustained operation. Here, we present a systematic investigation of degradation using X-ray tomographic microscopy, capturing the evolution of membrane delamination and anode catalyst layer damage as a function of current density and passed charge. Our results demonstrate that membrane delamination strongly depends on current density, while anode catalyst layer degradation scales with cumulative charge, highlighting distinct degradation pathways within the membrane-electrode assembly. To mitigate these effects, we engineer porous anion exchange layers to enhance CO₂ back-diffusion and relieve interfacial gas pressure. Among several architectures, a microporous anion exchange layer fabricated via nanoparticle-ionomer spray coating shows the most effective suppression of both membrane delamination and anode catalyst layer damage, while achieving high current densities and improved faradaic efficiency for CO production. These findings establish gas transport engineering within the bipolar membranes as a critical design lever for achieving durable and efficient CO₂ electrolysis.