Three Mechanisms for Protecting the PEM Fuel Cell Membrane, Plates and Catalyst

摘要

Performance of the perfluorinated sulfonic acid polymer electrolyte membrane in PEM fuel cells degrades through a multi-step process. Hydroxyl radicals, formed via crossover gases or reactions of hydrogen peroxide with Fenton-active contaminants, generate hydrogen radicals that attack the backbone of Nafion causing the release of fluoride anions. Fluoride anions promote corrosion of the plates and catalyst, with the release of transition metals into the fuel cell environment. Transition metal ions catalyze the hydroxyl attack on the Nafion backbone, resulting in further release of fluoride anions. We present here a new approach for mitigating the membrane degradation and for increasing the overall durability of the fuel cell by interfering with three steps of the membrane degradation cycle: the use of (i) hydroquinones to neutralize hydroxyl radicals, (ii) aza-crowns for sequestering fluoride anions, and (iii) crown ethers to sequester base metal cations.