Crosslinked Polybenzimidazoles Containing Functional CrosslinkersAs High-Temperature Proton Exchange Membranes: Enhanced Strength and Conductivity

Abstract

In the present work, a cross-linked high-temperature proton exchange membrane based on poly [2, 2′-(p-oxydiphenylene)-5, 50-benzimidazole] (OPBI), imidazole (Im) and hexachlorocyclotriphosphazene (HCCP) was prepared and characterized, aiming at their future application in fuel cell devices. The composite membranes were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray (EDX) and thermogravimetric analysis (TGA). The results show that the PBI are successfully cross-linked by the cross-linking agent, and the membranes are uniform and compact, with excellent thermal stability. Phosphoric acid (PA) doped crosslinked membranes have excellent mechanical properties and proton conductivities. The tensile strength of PA-doped PBI-ImCCP-20% at room temperature is 20 MPa, and the proton conductivity reaches 53 mS cm−1 at 160 °C without humidification. H2/O2 fuel cell assembled with PA-doped PBI-ImCCP-20% membrane delivered a peak power density of 749 mW cm−2 at 160 °C under anhydrous conditions. The excellent performance of PBI-ImCCP series cross-linked membranes makes them potential candidate for HT-PEMFC applications.