Antioxidant Strategies for Hydrocarbon-Based Membranes

The protection of polyarylene type hydrocarbon ionomers against radical induced degradation in the fuel cell is a daunting task, as radicals, notably HO*, react very rapidly with aromatic compounds. Therefore, radical quenching, even by more advanced scavengers than Ce3+, is rather ineffective. Therefore, alternative strategies for polymer stabilization need to be devised. We propose to focus on repairing intermediates of the polymer formed upon radical attack using a direct or mediated approach based on H2O2 as reducing agent. A kinetic model is used to identify minimum rate constants for repair reactions and requirements of the lifetime of polymer intermediates to achieve a target lifetime improvement of the ionomer. The results can help develop experimental approaches to implement such concepts, keeping in mind the challenge of avoiding side-reactions, loss or degradation of additives, and other adverse effects, such as catalyst poisoning.