Unstructured Pore Network Modeling with Heterogeneous PEMFC GDL Porosity Distributions

This is the first investigation of the liquid water saturation profile dependence on empirically determined heterogeneous polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layer (GDL) porosity distributions. An unstructured, two-dimensional pore network model using an invasion percolation algorithm is presented. Random fiber placements are based on the heterogeneous porosity distributions of six commercially available GDL materials recently obtained through X-ray-computed tomography visualizations. The pore space is characterized with a Voronoi diagram, and simulations are performed with a single inlet liquid water cluster. Saturation profiles are also computed for GDLs with uniform, sinusoidal, and square-wave porosity distributions. Liquid water tends to accumulate in regions of high porosity due to the associated lower capillary pressures. The results of this work suggest that GDLs tailored to have smooth porosity distributions have fewer pockets of high saturation levels within the bulk of the material. Finally, a study on theoretical surface modifications demonstrates that low porosity surface treatments at the catalyst interface result in greatly reduced overall saturation levels of the material.