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To advance the technology of polymer electrolyte membrane fuel cells, material development is at the forefront of research. This is especially true for membrane electrode assembly, where the structuring of its various layers has proven to be directly linked to performance increase. In this study, we investigate the influence of the various ingredients in the cathode catalyst layer, such as ionomer content, catalyst loading and catalyst type, on the oxygen and ion transport using a full parametric analysis. Using two types of catalysts, 40 wt.% Pt/C and 60 wt.% Pt/C with high surface area carbon, the ionomer/carbon content was varied between 0.29–1.67, while varying the Pt loading in the range of 0.05–0.8 mg cm−2. The optimum ionomer content was found to be dependent on the operating point and condition, as well as catalyst loading and type. The data set provided in this work gives a starting point to further understanding of structured catalyst layers.

A novel ex situ method of investigating the water transport in porous media for PEM fuel cells with an environmental scanning electron microscope (ESEM) is introduced. By applying two different experimental methods, a liquid water pressure gradient is created which is necessary for the liquid water transport in porous media. The first method relies on water condensation on the bottom surface of the GDL to introduce a liquid phase into the porous media. The second method applies an external pressure gradient. The relevance of the methods is shown by visualizing the water formation and transport in different GDL materials with the high spatial resolution of an ESEM. In all experiments, the fingering effect, proposed by other researchers could be confirmed. However, the water formation on the surface of the GDLs is not consistent with the common idea of water formation in GDLs. The methods were also used to investigate the advantageous effect of laser perforating GDLs on fuel cell performance. The water transport visualization near a hole of a laser perforated GDL supports the assumptions of lower liquid water saturation in the GDL (due to effective water transport in the channels), and larger in-plane water transport towards the perforations

In order to model the liquid water transport in the porous materials used in polymer electrolyte membrane (PEM) fuel cells, the pore network models are often applied. The presented model is a novel approach to further develop these models towards a percolation model that is based on the fiber structure rather than the pore structure. The developed algorithm determines the stable liquid water paths in the gas diffusion layer (GDL) structure and the transitions from the paths to the subsequent paths. The obtained water path network represents the basis for the calculation of the percolation process with low calculation efforts. A good agreement with experimental capillary pressure-saturation curves and synchrotron liquid water visualization data from other literature sources is found. The oxygen diffusivity for the GDL with liquid water saturation at breakthrough reveals that the porosity is not a crucial factor for the limiting current density. An algorithm for condensation is included into the model, which shows that condensing water is redirecting the water path in the GDL, leading to an improved oxygen diffusion by a decreased breakthrough pressure and changed saturation distribution at breakthrough.