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Theoretical Study on Chemical Degradation Mechanism of Nafion Side Chain by the Attack of OH Radical in Polymer Electrolyte Fuel Cell

We theoretically analyzed the chemical degradation mechanism of Nafion side chain by OH radicals on the basis of density functional theory calculations. We found that the cleavage of the C–O bond in ether groups is a main pathway of the degradation from the Nafion side chain by OH radicals under well-hydrated condition. The ether group, which is located near the sulfo group, is vulnerable to the OH radical attack rather than the other ether group connecting the side chain with the polymer main chain.