The Effect of Heteropoly Acids on Stability of PFSA PEMs under Fuel Cell Operation

Membranes were cast from mixtures of the 3M perfluorinated sulfonic acid ionomer [side chain -O-(CF2)4-SO3H] and various heteropoly acids (HPAs) at a 10 or 20wt% doping level. Membrane electrode assemblies (MEAs) fabricated from these membranes were subjected to a fuel cell testing protocol from 70 to 100 deg C under relatively dry conditions, dew point of 70 deg C, to avoid leaching of the HPA. The most significant finding was that the more stable HPAs, H4SiW12O40, -H3P2W18O62, and H6P2W21O71, reduce the rate of F- by over half and improve the power of the MEA by 9% under these conditions.