Pore Network Analysis of Capillary Water Transport in Porous Transport Layers of Polymer Electrolyte Membrane Fuel Cells

This study investigated the two-phase transport of water in hydrophobic porous transport layers (PTLs) of PEMFCs. The goal of this study is to clarify the electrode flooding phenomena and to improve water management. A steady multi-layer pore network model was developed to analyze the transport of liquid water in the PTL, which consisted of the microporous layer (MPL) and the gas diffusion layer (GDL) with different pore sizes. In addition, the gas diffusion through the partially-saturated pore network was calculated after steady water saturation distribution in the PTL was established. The results showed that a thicker MPL facilitates the merging of the water transport paths via active capillary fingering, which in turn reduces both the number of breakthrough sites out of the MPL and the water content in the GDL. It was also found that there exists an optimal MPL thickness whereby maximum diffusion rate can be achieved in the multi-layer PTLs.