Preparation of Ether-free Polycarbazole-Based Anion Exchange Membranes and Regulation of Cations on Membrane Properties and Fuel Cell Performance

Quaternized ether-free aromatic polymers from superacid-catalyzed polycondensation are excellent candidates for high-performance anion exchange membranes (AEMs). Most current studies mainly focus on cation-modified carbon-aromatic AEMs. However, the structure–property relationship of cation-functionalized heteroaromatic polyarylene systems is still insufficiently understood. This work develops a series of carbazole-based ether-free AEMs with different side-chain quaternary ammonium (QA) cations, including conventional trimethylammonium, charge-delocalized imidazolium, and N-cyclic piperidinium and quinuclidinium. All membranes share the same polycarbazole backbone. Thus, the side-chain cation structure primarily determines membrane comprehensive performance. QPC-TMA with trimethylammonium groups exhibits the highest hydroxide conductivity at 80 °C, owing to its high ion exchange capacity and well-developed microphase separation. In comparison, QPC-QUI with bulky quinuclidinium groups shows outstanding alkaline and oxidative stability under harsh aging conditions. It shows least conductivity loss (2.65% loss for 1080 h) and weight loss (0.81% loss for 72 h).In fuel cell tests, the QPC-QUI-based AEM achieves a peak power density of 998 mW cm–2, which is higher than QPC-TMA (928 mW cm–2). This work proves that rational cation structural design of ether-free heteroaromatic polymers is a reliable strategy to prepare high-conductivity and durable AEMs for electrochemical energy applications.