Radical-induced degradation mechanism of perfluorinated polymer electrolyte membrane

The degradation mechanism induced by radicals was investigated for Nafion®-117 by solution analysis. Nafion® was exposed independently to three kinds of radicals, OH, H and O2− which were produced separately by γ-irradiation. Based on the eluted elements, the scission site in the membrane was analyzed. The results showed that the scission site was classified into two and these locations were closely relating to oxidative and reductive reactions. The decreasing rate of proton conductivity was more significant under the influence of reductive radicals. The progression of the unzipping reaction of main chain was suggested to be initiated by the production of tertiary carbon radical by reductive radicals such as H and O2− with the aid of OH. The structural degradation such as collapse of cluster and the cluster decomposition as well as the performance degradation was found to be initiated by such reductive radicals.

► Degradation process of Nafion was investigated by exposing to oxidative and reductive radicals separately with the aid of γ-irradiation. ► The location of dissociation of the membrane due to radicals was clearly different according to the redox ability. ► The decrease of proton conductivity was observed more significantly for the sample exposed to reductive radicals. ► The cluster structure of Nafion was found to be more damaged by reductive radicals.