Pore Network Modeling of Hydrophilic / Hydrophobic Composite Microporous Layers for Polymer Electrolyte Fuel Cells

Abstract

Liquid water accumulated in the catalyst layer (CL) and gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC, PEMFC) results in performance deterioration due to the inhibition of oxygen transport to the cathode CL (Flooding). To enhance the drainage in the GDL, a microporous layer (MPL) employed at the CL side of the GDL substrate is effective[1, 2]. Hydrophilic/hydrophobic composite MPLs in-house applied have mitigated the flooding [3], while the mechanism was not well clarified. A pore network model (PNM) [4, 5] of in-house hydrophobic MPLs constructed with focused ion beam scanning electron microscope (FIB-SEM) observations and validated with convective air permeation and oxygen diffusion measurements with changing wetting liquid saturation (Galwick, Porous Materials Inc., USA)[6] is modified for the analysis of the composite MPL.AcknowledgmentsThanks are offered to Professor Kohei Ito of Kyushu University for valuable discussions.