Polybenzimidazole Fuel Cell Technology: Theory, Performance, and Applications

Abstract

After approximately 15 years of development, polybenzimidazole (PBI) chemistries and the con- comitant manufacturing processes have evolved into commercially produced membrane electrode assemblies (MEAs). PBI MEAs can operate reli- ably without complex water humidification hard- ware and are able to run at elevated temperatures of 120–180 ? C due to the physical and chemical robustness of PBI membranes. These higher tem- peratures improve the electrode kinetics and con- ductivity of the MEAs, simplify the water and thermal management of the systems, and signifi- cantly increase their tolerance to fuel impurities. Membranes cast by a newly developed poly- phosphoric acid (PPA) process possessed excel- lent mechanical properties, higher phosphoric acid (PA)/PBI ratios, and enhanced proton con- ductivities as compared to previous methods of membrane preparation. The p-PBI and m-PBI are the most common polymers in PBI-based fuel cell systems, although AB-PBI and other derivatives have been investigated. This chapter reports on the chemistries and sustainable usages of PBI- based high temperature proton exchange mem- brane fuel cells (PEMFCs).