High Strength and Stable Proton Exchange Membrane Based on Perfluorosulfonic Acid/Polybenzimidazole

In this work, a series of high strength, thermal stable and antioxidant proton exchange membranes were designed with solution processible polybenzimidazole (PBI) as the matrix and perfluorosulfonic acid (PFSA) as the fortifier for proton exchange. Solution processible PBI was successfully synthesized by introducing 4,4′-dicarboxydiphenyl ether into the molecular chains of PBI. PFSA/PBI composite membranes were obtained by solution blending and film casting. PBI and PFSA/PBI composite membranes exhibited greatly enhanced tensile strength and Young’s modulus compared to PFSA. PFSA/PBI composite membranes are stable below 300 °C which are suitable for practical application in proton exchange membrane fuel cells. The PFSA/PBI composite membranes show good dimensional stability with low water uptake and swelling rate. The PFSA/PBI composite membranes also exhibit excellent antioxidation stability with less than 5% initial mass loss over 120 h in Fenton reagent. The proton conductivity of PBI is greatly enhanced by blending with PFSA and the proton conductivities of the composite membranes are increased with the raise of PFSA content and temperature. This work offers valuable insights into the exploration of PBI based highperformance proton exchange membranes.