The local saturation in porous transport layers (PTL) has been determined using synchrotron-based x-ray micro-tomography. The water distribution inside the porous structure could be resolved on the scale of the pores. After phase segmentation of the image data, the measurement of the liquid saturation as function of the through plane coordinate of the PTL and the capillary pressure was possible. For verification, first experiments with complete cells are also shown.

Channel‐to‐channel cross convection in serpentine flow fields of polymer electrolyte fuel cells (PEFC) can influence the overall cell performance. The effect strongly depends on the gas transport properties of the gas diffusion layer (GDL). For the first time measured anisotropic, compression dependent permeability and effective diffusivity of GDLs are used to quantify the influence of cross convection on the local current distribution and performance. A model was developed to examine different channel‐rib geometries and GDL characteristics. The results show that cross convection can significantly increase the current density and consequently the power density of PEFCs. A strong sensitivity to GDL compression, flow velocity and rib width was found. As an optimised case the GDL thickness under the rib was increased resulting in about 20% higher current densities. Precise knowledge of the GDL characteristics and its compression are key to understand channel‐to‐channel cross convection and optimise perfomance.