Analysis of Two-Phase Transport in Ultra-Thin Catalyst Layer Based Electrodes Using a Mixed Wettability MPL Model

A new approach to analyze two-phase water transport in microporous layer used on polymer electrolyte fuel cells is presented. The effect of mixed wettability in MPLs is studied by means of a novel pore-size distribution (PSD) model, which is used to estimate saturation, liquid relative permeability, gas relative permeability, liquid-vapour interfacial surface area, and total pore surface area. With the proposed model, micro-structural information of the MPL often neglected by older models is taken into consideration, without adding the burden of large-scale computations usually associated with pore network models and Lattice-Boltzmann methods. The model is applied to study the effects of mixed wettability on ultra-thin catalyst layer fuel cells, where two-phase flow plays a key role.