Effects of conjoint mechanical and chemical stress on perfluorosulfonic-acid membranes for fuel cells

To improve the lifetime of proton-exchange membrane (PEM) fuel cells, it is necessary to provide a better understanding of the degradation mechanisms of the perfluorosulfonic acid (PFSA) membranes during fuel cell operation. Despite quantities of work focusing independently on chemical or mechanical degradation, only a few concerned the effect of both combined. The purpose of this study is to analyze the effects of conjoint chemical and mechanical stress on PFSA membranes via an ex-situ approach. First, an investigation of the effects of chemical degradation by radical attacks (i.e. exposure to Fenton reagents) on PFSA membranes was carried out. The results confirm that the chemical decomposition of PFSA membranes is significantly influenced by the concentration of Fenton's reagents, both chemically and morphologically. Second, a custom-made device was developed to examine the impact of coupled chemical and mechanical degradations. The initial results show that fully hydrated membranes seem to withstand severe sinusoidal constraints as no crack formed. However, the application of cyclic compression resulted in accelerated chemical decomposition of PFSA membranes. The results also demonstrate that some microstructural changes can appear and lead to a slight increase in the hydrogen crossover that can be detected before it impacts the cell performances.