Porous Aromatic\nFramework with Imidazole Group-Reinforced\nHigh-Temperature Proton Exchange Membrane with Promoted Proton Transport\nEfficiency and Power Density

The plasticizing effect leading to a marked deterioration\nin mechanical\nproperties and a substantial leakage of phosphoric acid (PA), which\noccurs at a high PA-doping level, is a critical challenge for polybenzimidazole\n(PBI) high-temperature proton exchange membranes (HT-PEMs) doped with\nPA (PA–PBI). The plasticizing effect leading to a marked deterioration\nin mechanical properties and a substantial leakage of PA, which occurs\nat a high PA-doping level, is a critical challenge for PA−PBI\nmembranes. In this study, novel porous aromatic frameworks framed\nwith imidazole groups were synthesized, which can afford extra proton\ntransport sites and develop a perfect hydrogen bonding network with\nPA. The obtained HT-PEM-doped poly[4,4′-(diphenyl ether)-5,5′-bibenzimidazole]\n(OPBI) with 10% PAF-226-PA exhibited a tensile strength of 116.5 MPa,\na proton conductivity of 0.17 S cm<sup>–1</sup> at 200 °C,\nand a peak power density of 641.57 mW cm<sup>–2</sup> with\na catalyst Pt/C loading of merely 0.3 mg cm<sup>–2</sup>, demonstrating\ngood potential for application in HT-PEM fuel cells. The formed hydrogen\nbond network enhanced proton mobility and helped retain the PA, mitigating\nthe PA loss, enhancing the interfacial interaction between PAF-226-PA\nand OPBI, and thus improving the electrochemical and mechanical performance\nof HT-PEMs for high-performance, high-temperature fuel cells.