Heteropoly Acid Functionalized Membranes for High Performance and Chemically Stable Fuel Cell Operation

Chemical degradation of perfluorinated sulfonic acid membranes, such as Nafion via radical attack represents one of the current challenges with fuel cell durability. Ce and Mn have been used to decompose radicals, but migration of these species results in loss of chemical stability efficacy. Herein we report on a recent breakthrough in chemical durability that has been achieved through using heteropoly acids (HPAs) as both the proton conducting acid and the radical decomposition catalyst. Exceptional chemical durability is reported for a thin film and a mechanism is proposed where the W atoms in the HPA reversibly change oxidation state from W(VI) to W(V) while decomposing radical species. It is concluded that covalently tethered HPA should be considered as a next generation chemical stabilization strategy for polymer electrolyte fuel cells.