Possible Repair Mechanism for Hydrocarbon-Based Ionomers following Damage by Radical Attack
- Journal Article
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Polymer electrolyte fuel cell (PEFC) membranes are subject to radical-induced degradation. Antioxidant strategies for hydrocarbon-based ionomers containing aromatic units can focus on intermediates that are formed upon attack by hydroxyl radicals (HOcenterdot). Among the different intermediates, the cation radical Pcenterdot+ is the most promising target for repair, for example by cerium(III). For the "repair" reaction of Ce(III) with radicals of a poly(α-methylstyrene sulfonate) oligomer we determined an activation energy of (9 ± 2) kJ mol−1 and a rate constant of 1.6 centerdot 108 M−1 s−1 at 80 °C by pulse-radiolysis. For the reduction of Ce(IV) by hydrogen peroxide the activation energy was determined by stopped-flow as (30 ± 1) kJ mol−1 with a rate constant of 4.8 centerdot 106 M−1 s−1 at 80 °C. These parameters are fed into a kinetics model to estimate the efficacy of the cerium (III)/(IV) redox couple as a catalytic repair agent in hydrocarbon-based fuel cell membranes. While cerium can mitigate polymer degradation, repair efficacy depends on the polymer degradation pathway and the nature and lifetime of the intermediates. Show more
Journal / seriesJournal of the Electrochemical Society
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