Interactions between reinforced membrane durability and gas diffusion layer and flow field plate designs in fuel cells
Yixuan Chen, Nitish Kumar, MohammadAmin Bahrami, Francesco P. Orfino, Monica Dutta, Michael Lauritzen, Esmaeil Navaei Alvar, Erin Setzler, Alexander L. Agapov, Erik Kjeang
Abstract
Composite membranes reinforced with expanded polytetrafluorethylene (ePTFE) have been increasingly adopted over conventional non-reinforced membranes in fuel cell applications. In this work, a state-of-the-art ePTFE reinforced membrane is subjected to combined chemical and mechanical degradation until failure to assess and identify failure modes. Sample failure analysis is affected by 4D in-situ imaging with an X-ray computed tomography system, which is a non-invasive 3D visualization technique that can capture membrane morphological changes pertaining to the degradation. Crack development in the catalyst layer and membrane planes, as well as global membrane thinning are the universal failure modes identified in the active area, which are strongly dependent on the interactions between catalyst coated membrane and gas diffusion layer (GDL) and flow field plate. Catalyst layer and membrane cracks are all found under the flow channels, and are highly correlated to natural surface features in the GDL; while locally elevated membrane thinning is observed at locations with higher compression such as the flow field land. Despite the membrane degradation observed, the ePTFE reinforcement layer retains its integrity from both chemical and mechanical degradation, resulting in substantially improved durability. Additional durability benefits are demonstrated with thick microporous layers and wide lands.