Porphyrin Helical Nanochannel‐Assembled Polybenzimidazole Membranes Doped with Phosphoric Acid for Fuel Cells Operating in a Temperature Range of 25–200 °C

Abstract High‐temperature proton‐exchange membrane fuel cells (HT‐PEMFCs) fabricated with phosphoric acid (PA)‐doped polybenzimidazole (PBI) show apparent technical advantages. In practical automotive applications, achieving cold start‐up capability is crucial. In this work, a kind of branched block proton exchange membrane (PEM) based on PBI with a low content of porphyrin ring (<1 mol.%) is reported as a branched monomer. Self‐assembly into high‐density helical nanochannels under the synergistic effect of phase separation and porphyrin π−π stacking, thus the PEM can maintain a high level of PA doping. Specifically, the PA/1.8TCPP‐BrPy‐OPBI membrane shows a proton conductivity of 0.169 and 0.071 S cm⁻¹, as well as an H₂‐O₂ fuel cell peak power density of 1077 and 357 mW cm⁻² at 180 and 80 °C without humidification and backpressure, respectively. The membrane electrode assembly (MEA) can exhibit good fuel cell stability, with a voltage decay rate of only 7.0 µV h⁻¹ at 80 °C. Furthermore, it maintains a peak power density of 93% even after 150 start‐up/shut‐down cycles at 25 °C. This work expands the operating temperature range of conventional PBI membranes between 25 and 200 °C and thus provides a novel strategy for high‐performance PBI‐based HT‐PEMFCs.