Anion exchange membranes (AEMs) have garnered attention as promising materials for electrochemical devices such as fuel cells and electrolyzers.[1] Since AEMs are used in an alkaline environment, chemical stability is essential. In order to solve this problem, many research groups have developed polyphenylene-based polymers and report excellent chemical durability.[2-4] However, the electrochemical performance of AEMs can be influenced by various environmental factors, including carbon dioxide (CO₂).[5] In this study, we investigate the effect of CO₂ on the properties and performance of polyphenylene-based AEMs.

Polyphenylene-based AEMs were synthesized through a C-C coupling reaction using a Nickel catalyst. The membranes were prepared by solution casting. To investigate the effect of CO₂ on membrane properties, the ion conductivity was monitored while flowing CO₂/Argon mixed gas. Membrane properties such as ion exchange capacity (IEC), water uptake, swelling ratio, and ion conductivity were characterized to correlate with CO₂ poisoning behavior.

Our results show that the presence of CO₂ significantly affects the properties and performance of the AEMs. The CO₂ molecules were found to interact with the quaternary ammonium groups of the AEMs, leading to a decrease in ion conductivity. Overall, our findings demonstrate the importance of considering the effect of CO₂ on AEMs when designing and operating electrochemical devices that utilize these materials. This study provides valuable insights into the behavior of poly(phenylene)-based AEMs in CO₂-rich environments and paves the way for further research on developing CO₂-resistant AEMs.