Proton exchange membrane (PEM) fuel cells are promising for clean and efficient energy conversion across diverse applications. High-temperature PEM fuel cells (HT-PEMFCs) using phosphoric acid (PA)-doped polybenzimidazole (PBI) can operate up to 200°C, but at lower temperatures, water-induced PA loss often leads to performance degradation and reduced durability. In this work, we present a new class of main-chain ion-pair PBI membranes by integrating the imidazolium-biphosphate ion-pair units directly into the PBI backbone. This design results in membranes with high acid content, stronger acid-polymer interactions and stabilized acid retention. In single-cell tests, the Im+-PBI15-3 wt.% exhibits peak power densities of 0.79 W cm−2 at 160°C and 0.57 W cm−2 at 120°C, with excellent durability and minimal acid loss over prolonged operation. These results demonstrate that main-chain ion-pair PBIs offer a robust, high-performance solution for HT-PEMFC membranes capable of efficient operation down to 120°C.
Lin et al. (Thu,) studied this question.