Reinforced Membrane Durability in Proton Exchange Membrane Fuel Cell Stacks for Automotive Applications

Abstract

A key requirement for automotive proton exchange membrane fuel cell stacks is improved performance and durability. High-performance can be delivered using perfluorosulfonic acid (PFSA) membranes that are thin and have low equivalent weight (920). Initial durability in a single cell confirmed edge protection films prevent premature membrane electrode assembly (MEA) failure. This allowed the true MEA durability to be assessed in 30-cell stacks. Based on physical leak tests and open-circuit voltage (OCV) decay rates a Johnson Matthey Fuel Cells (JMFC) reinforced membrane provided a sixfold improvement in durability compared to commercially available nonreinforced membranes. The improved durability is ascribed to increased dimensional stability during hydration/dehydration and an improved resistance to tear propagation. The commercial membranes fail mechanically, accelerated by chemical attack of the ionomer. The reinforced membrane is mechanically robust and fails due to removal of the PFSA ionomer from the reinforcement by chemical attack. Accelerated OCV hold tests with hydrocarbon membranes confirmed the chemical attack was from the radicals generated by and gas crossover through the membrane. Adding a decomposition catalyst to the JMFC reinforced membrane significantly extended the membrane lifetime at OCV, suggesting was the major source of the damaging radicals. The automotive durability target of should be achievable using the JMFC reinforced membrane containing the decomposition catalyst.