Proton conducting membranes based on benzimidazole sulfonic acid doped sulfonated poly(oxadiazole-triazole) copolymer for low humidity operation

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 T_g 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.