Membrane Degradation Mechanisms and Accelerated Durability Testing of Proton Exchange Membrane Fuel Cells

Abstract

Molecular H2 and O2 reacting on the surface of Pt catalyst to form the membrane degrading species is the dominating membrane degradation mechanism in PEMFCs; not the formation of active oxygen species from H2O2 decomposition or the direct formation of active oxygen species in the oxygen reduction reaction. The source of H2 or O2 is from the reactant crossover through the membrane. The reaction mechanism is chemical in nature and depends upon the catalyst surface properties and the relative concentrations of H2 and O2 at the catalyst. The membrane degradation rate also depends on the residence time of the species in the membrane and the volume of the membrane. The sulfonic acid groups in the Nafion side chain are key to the mechanism by which the radical species attack the polymer.