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

摘要

Molecular H_2 and O_2 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 H_2O_2 decomposition or the direct formation of active oxygen species in the oxygen reduction reaction. The source of H_2 or O_2 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 H_2 and O_2 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.