Advancements in Ether-free Poly(arylene) Proton Exchange Membranes: Pyridine and Piperidine-Based Architectures for High-Temperature Fuel Cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) provide a number of benefits over low-temperature systems, including improved reaction kinetics and a greater ability to tolerate impurities. However, developing durable membranes remains a key challenge due to the competing demands of phosphoric acid (PA) retention, thermal stability, and high proton conductivity in the absence of excessive PA doping. While polybenzimidazole (PBI) membranes demonstrate strong performance, their susceptibility to mechanical degradation and oxidative instability at high temperatures have spurred the search for superior alternatives. This review highlights pyridine/piperidine-based membranes as a promising solution, leveraging heterocyclic additives (e.g., pyridine and piperidine) to enhance durability and functionality. Key chemical modifications including side-chain and main-chain adjustments are examined for their influence on the polymer structure and performance. Additionally, the microporous architecture and intermolecular interactions between functional groups are analyzed to elucidate their roles in improving the conductivity and stability. Compared to commercial PBI membranes, pyridine/piperidine-based alternatives exhibit superior performance stability, positioning them as strong candidates to advance HT-PEMFC technology toward sustainable energy applications.