Proton Conducting Membranes Based on Benzimidazole Sulfonic Acid Doped Sulfonated Poly(Oxadiazole-Triazole) Copolymer for Low Humidity Operation

Abstract

This work reports for the first time the preparation of sulphonated poly(oxadiazole-triazole) copolymer membranes doped with amphoteric molecule, 1H-benzimidazole-2-sulphonic acid and their characterisation as proton conductors at 120 °C and low humidity. The membranes had not only high proton conductivities, up to 4 × 10-3 S cm-1 at 120 °C and low relative humidity (5 and 10%), but also had good mechanical properties with a storage modulus of about 3 GPa at 300 °C and high thermal stability with Tg up to around 420 °C. Because of their superior ion conducting and mechanical properties they have potential as a proton conducting membrane for fuel cell applications, in particular at high temperature and extremely low-humidity conditions.