Effect of Microporous Layer Cracks on Catalyst Durability of Polymer Electrolyte Fuel Cells for Heavy-Duty Applications

Polymer electrolyte fuel cells (PEFCs) have demonstrated great potential in heavy-duty vehicles (HDVs) due to their unique scalability and smaller additional weight penalty for a longer driving range. To enable the deployment of HDVs, an increased durability of platinum (Pt), which is the catalyst used in PEFCs, and the understanding of degradation mechanism are the top priorities. In this study, different configurations of cracks were introduced into the microporous layer (MPL) of membrane electrode assemblies (MEAs) and accelerated stress tests (ASTs) simulating HDV lifetime were performed. The electrochemical characterization of the MEAs with and without MPL cracks demonstrated similar durability trends. Cracks in the MPLs do not significantly improve the performance of the cell. However, identical location mu-X-ray fluorescence (mu-XRF) spectroscopy performed on the MEAs showed significant in-plane movement of Pt over the course of AST, especially for the MEAs with vertical cracks in the MPLs. It is indicative that cracks in the MPLs can have a negative impact on the PEFCs' durability because of them being filled with water promoting Pt transport. The modeling study showed water distribution and oxygen transport through the MPL with cracks.