Fabrication of Composite Membrane Based on Silicotungstic Heteropolyacid Doped Polybenzimidazole for High Temperature PEMFC

Stable proton conducting composite membranes (CM1-CM3) based on polybenzimidazole (PBI) and various weight percent (35, 50 and 65 wt %) of inorganic hetero poly acids (IHA) were prepared by dissolving PBI in methanesulfonic acid and required amount of IHA was then added to PBI solution. IHA were prepared by acid-catalyzed condensation of various ratios of silicotungstic acid (TSA) (35, 50 and 65 wt %) and silica (TEOS) (65, 50 and 35 wt %) using sol-gel procedure. These materials were characterized morphologically, studied their intrinsic structures and intimate relation with proton conductivity. It was found that thermal properties and proton conductivity of the composite membrane are strongly dependent on the IHA which increased with increase of IHA content. The composite membrane containing 65 wt % of IHA showed highest thermal property and proton conductivity. Composite membrane containing 65 wt% of IHA displayed highest conductivity of 2.91x10-1 S/cm at 150 °C. Thus introduction of IHA into PBI matrix is an efficient route to improve thermal properties and proton conductivity of PBI.