Laboratory assessments applied to mass-produced automotive fuel cells

To meet the required useful life targets of proton exchange membrane fuel cells (PEMFC) for long haul and heavy-duty applications, the degradation mechanisms and influences from production need to be analyzed and reduced. Therefore, new and aged PEMFCs should be examined on a macro- and microscopic scale. The purpose of this work is to analyze fuel cells from series production and compare the findings with literature. Since most of the results from literature base on laboratory cells, this research closes the gap between lab-scale experiments and large-scale production. Thereto, the bipolar plates and membrane electrode assemblies of the fuel cells of the Toyota Mirai II and the Hyundai Nexo fuel cell vehicles were examined using optical and scanning electron microscopes. Additionally, energy-dispersive X-ray spectroscopy was performed. Differences in flow fields (channel dimensions, water management), layer and membrane thicknesses, surface porosities, contact angels and layer surface conditions were investigated. Comparisons with current literature provide an opportunity to estimate the influences of the observed structures. In addition, a methodology is developed to map temperatures that result in the discoloration of the titanium bipolar plates during abusive operation.