Predicting Membrane Lifetime with Cerium Oxide in Heavy Duty Fuel Cell Systems

Abstract

Stringent reliability and durability requirements for fuel cells in heavy duty vehicles demand highly durable ionomer membranes. Fuel cell membranes degrade chemically and mechanically during operation, which can lead to membrane thinning, pinhole and crack formation and eventual failure due to hydrogen leaks. The chemical portion of degradation can be suppressed with the use of radical scavenging agents such as cerium oxide. In order to implement extended durability solutions in actual field operation, however, aptly designed accelerated durability tests and empirical models are needed to predict membrane lifetime under various operating conditions, while also considering additive stability over time. Here, an empirical membrane lifetime model recently developed for transit bus applications is modified and demonstrated to predict membrane lifetime with cerium oxide incorporated into the membrane electrode assembly as a chemical stabilizer. The lifetime prediction approach utilizes laboratory scale experimental data from an accelerated membrane durability test complemented by measured cerium washout rates. Provided that the cerium washout rates were relatively low, the predicted membrane lifetime of cerium supported membranes was found to significantly exceed the ultimate 25,000 h heavy duty durability target.