Novel Polybenzimidazole-Phosphoric Acid Membranes for Fuel Cell Applications

Abstract

Polybenzimidazole-phosphoric acid membranes have been used extensively in high temperature fuel cell applications. They are generally prepared either by copolymerization of tetramines and dicarboxylic acids (AA/BB copolymers) or by homopolymerization of diaminoacids (AB homopolymers). We describe the preparation of 4-(3,4-diaminophenylsulfonyl) benzoic acid, a diamino acid useful for the synthesis of novel AB polybenzimidazoles having excellent thermal and thermal-oxidative stability. The polymer, readily cast from polar aprotic solvents, when imbibed with phosphoric acid produces polymer electrolyte membranes exhibiting proton conductivities ranging from 0.06-0.12 S/cm at 80-160 {degree sign}C (20% RH) at a phosphoric acid doping level of 6.1.

Diluted Thermopressurized Phosphoric Acid: A Gentle Proton Donor for Polysaccharide Acid Depolymerization and (Bio)processing

“…[E] In order to increase temperature resistance, a thermostable HT-PEMFC was built on polybenzimidazole previously doped with phosphoric acid. A range of 0.06-0.12 S cm −1 was achieved [59,60].…”