Porous Aromatic Framework with Imidazole Group-Reinforced High-Temperature Proton Exchange Membrane with Promoted Proton Transport Efficiency and Power Density
Xinyi Zong, Liying Wang, Haina Mi, Yuhan Liu, Jing Li, Baijun Liu, Wei Hu, Weiwei Cai, Chunzhu Jiang
Abstract
The plasticizing effect leading to a marked deterioration in mechanical properties and a substantial leakage of phosphoric acid (PA), which occurs at a high PA-doping level, is a critical challenge for polybenzimidazole (PBI) high-temperature proton exchange membranes (HT-PEMs) doped with PA (PA–PBI). The plasticizing effect leading to a marked deterioration in mechanical properties and a substantial leakage of PA, which occurs at a high PA-doping level, is a critical challenge for PA−PBI membranes. In this study, novel porous aromatic frameworks framed with imidazole groups were synthesized, which can afford extra proton transport sites and develop a perfect hydrogen bonding network with PA. The obtained HT-PEM-doped poly[4,4′-(diphenyl ether)-5,5′-bibenzimidazole] (OPBI) with 10% PAF-226-PA exhibited a tensile strength of 116.5 MPa, a proton conductivity of 0.17 S cm –1 at 200 °C, and a peak power density of 641.57 mW cm –2 with a catalyst Pt/C loading of merely 0.3 mg cm –2, demonstrating good potential for application in HT-PEM fuel cells. The formed hydrogen bond network enhanced proton mobility and helped retain the PA, mitigating the PA loss, enhancing the interfacial interaction between PAF-226-PA and OPBI, and thus improving the electrochemical and mechanical performance of HT-PEMs for high-performance, high-temperature fuel cells.