Mass Transfer in Microporous Layers for Polymer Electrolyte Fuel Cells Analyzed with Pore Network Modeling

Abstract

The application of a microporous layer (MPL) to the catalyst layer (CL) side of the gas diffusion layer (GDL) substrate of a polymer electrolyte fuel cell (PEFC, PEMFC) is effective to mitigate liquid water accumulation at the CL that inhibits oxygen transport to the cathode CL (Flooding)[1, 2]. To elucidate the effects of two-phase flow on the oxygen transport in an MPL for its optimized designs, we have modeled three-dimensional porous structures of in-house hydrophobic MPLs with pore network models (PNMs)[3, 4] for convective air permeation and oxygen diffusion with liquid water saturation. Pore diameter distributions derived by a focused ion beam scanning electron microscope (FIB-SEM) are used to construct the PNMs. Oxygen diffusion measurements by using gas chromatography with changing wetting liquid saturation (Galwick, Porous Materials Inc., USA)[5], as well as air permeation measurements, validate the PNMs.AcknowledgmentsThanks are offered to Professor Kohei Ito of Kyushu University for valuable discussions.