Ageing mechanisms of proton exchange membrane used in fuel cell applications

Degradation processes of both sulfonated polyimide (sPI) and sulfonated polyetheretherketone (sPEEK) membranes were studied in-situ in fuel cells. Ex-situ ageing protocols were developed for both polymers and model compounds. On the one hand sulfonated polyimides are shown to be mainly sensitive to hydrolysis though an additional thermo activated oxidation process occurs in fuel cell conditions and at least accelerates the degradation. On the other hand sulfonated polyetheretherketone are insensitive to hydrolysis but greatly degraded in an oxidative medium.