Recent progress in proton conducting membranes for PEFCs

Recent progress in proton conducting membrane materials for high temperature polymer electrolyte fuel cells (PEFCs) is reviewed. Perfluorinated ionomers, hydrocarbon ionomers, and other miscellaneous materials are included. As a state,of-the-art material, perfluorinated ionomers have been mostly studied. The current research has focused on reinforcement (with porous support, fibril, fiber, or fabric) and chemical modification (by copolymerization or cross-linking). Considerable improvement has been achieved in the thermal, chemical and mechanical stability as well as the proton conductivity. The perfluorinated ionomer dispersed with nanoparticles of metal oxides and platinum has proved its potential availability as an electrolyte membrane for non-humidified operating PEFCs. As alternative membranes, non-fluorinated hydrocarbon materials have been a great challenge. Aromatic ionomers such as sulfonated polyimides and polyethers, or acid-doped polybenzimidazoles have been developed. Ionic liquids, organic/inorganic hybrids, and fullerene derivatives have also been described as a novel class of anhydrous proton conducting materials.