Synthesis and Characterization of Sulfonated Polybenzimidazole (SPBI) Copolymer for Polymer Exchange Membrane Fuel Cell

Abstract

A diverse sulfonated polybenzimidazole copolymer (SPBI) as proton exchange membrane was synthesiszed via one-step high temperature polymerization method with 3,3-diaminobenzidine (DABD), 5-sulfoisophthalic acid (SIPA), 4,4-sulfonyldibenzoic acid (SDBA) and biphenyl-4,4-dicarboxylic acid (BDCA). The SPBI membrane was prepared through a direct hot-casting and in situ phase inversion technique. Characterization tests were carried out on the membranes including surface morphology, distribution of elements on the membrane, determination of functional groups, thermal stability, ion exchange capacity, water uptake rate and proton conductivity. The as-synthesized SPBI membrane displayed a smooth surface via scanning electron microscopy (SEM) analysis which is thermally stable up to 443 °C. The SPBI membrane showed higher water uptake rate (WUR) and proton conductivity though it had lower ion exchange capacity (IEC) value compared to recast Nafion membrane. The proton conductivity of the SPBI membrane with IEC of 0.60 mmol/g was 4.50 × 10-2 S/cm at 90 °C. This study shows that the SPBI membrane has great potential in polymer exchange membrane fuel cell (PEMFC) applications.