Proton-exchange membrane or polymer-electrolyte membrane (PEM) fuel cells are becoming increasingly popular due to their versatility, high efficiencies and low pollutant output. One of the main failure modes of PEM fuel cells is the degradation of the polymer membranes, and therefore considerable research and resources are being committed to understand the important aspects of the process. One key degradation pathway is initiated by peroxide radical attacks at the membrane electrode interface; peroxides that are generated as the result of the associative oxygen reduction reactions when in contact with low concentrations of transition metal ion impurities. Previous work on the degradation of the Sandia developed sulfonated poly(phenylene) (SDAPP) membranes used solution 1H and 13C NMR to characterize the decomposition products However, the complicated chemistry of the full polymer led to inconclusive identification of all the resulting chemical species. The work described in this poster focuses on the intentional degradation of simpler constitutive model compounds that will ultimately lead to a better understanding of the degradation chemistry that occurs in SDAPP PEMs. These model compounds underwent testing with Fenton’s reagent, in which the compounds are directly exposed to varying concentrations of both H2O2 and trace ferrous iron contaminants. Solution 13C NMR is used to observe the decomposition as a function of time and identify the degradation products of each reaction at various temperatures. These results are then used to evaluate the degradation of the complete SDAPP membrane.

Chemical degradation of model sulfonated polyphenylene proton exchange membranes

255th National Meeting (2018)

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