Poly benzimidazoles as a Substitution for Nafion in High Temperature Proton Exchange Membrane Fuel Cells

In common low temperature fuel cells water acts as a charge carrier and transports proton ions along the membrane, so proton exchange membrane in these fuel cells should always kept in hydrated form. Therefore, a water management system especially for fuel cell stacks are needed to keep membrane in an optimum level of humidity. On the other hand, increasing the temperature of fuel cell increases the kinetic of reactions and consequently the efficiency of the cell. Increasing temperature causes drying of Nafion membrane and deteriorates its characteristics. So Nafion membrane won’t be suitable anymore and another polymer that tolerates high temperatures should be introduced. Polybenzimidazole doped with phosphoric acid as a proton conductor is a very good substituent because of its low cost and high mechanical strength. In this paper different structure of polybenzimidazoles and using them as high temperature proton exchange membrane was studied.