Mechanism of Perfluorsulfonic Acid Membrane Chemical Degradation Under Low RH Conditions

Chemical degradation of perfluorosulfonic acid (PFSA) membranes of proton exchange membrane (PEM) fuel cells is a well-known process which can limit PEM fuel cell lifetimes.1 Chemical degradation can weaken membranes to the point where they no longer provide an effective barrier to reactant gas permeation or electrical shorting. The chemical degradation of PFSA-based PEMs is initiated and propagated by the actions of a variety of oxidants formed during fuel cell operation including hydroxyl radical, hydroperoxyl radical and hydrogen peroxide. Of these oxidants, hydroxyl radical is the only oxidant capable of abstracting hydrogen atoms from carboxylic acid end groups that are the reactive functional groups of a degrading PFSA. Recently, the use of active, reversible hydroxyl radical scavengers such as Ce3+ an