Computational and Experimental Analysis of Water Transport at Component Interfaces in Polymer Electrolyte Fuel Cells

Abstract

This study investigated the influence of micro-porous layer (MPL) surface topology on the polymer electrolyte fuel cell (PEFC) performance through both experimental characterization and computational modeling. Studies were performed considering MPLs with varying degrees of surface roughness and crack size/density. In two instances, we systematically varied the topology by introducing water transport channels into the MPL. We experimentally observed that transport channels consistently increased the maximum current density. To investigate the reasons for the performance improvement, a two-dimensional, multi-phase, multi-fluid model was formulated with discrete domains for morphological features, including liquid water retention within interfacial voids and cracks. The model results provide evidence that the performance improvement with the modified MPLs is due to improved liquid water removal from the catalyst layer (CL). Liquid water moves laterally through the CL|MPL interface until it reaches the milled lines and from there it is removed in through-plane direction through the fibrous diffusion media (DM) and into the gas channel. A key outcome of this work is that we demonstrate a CL|MPL interface model that can accurately capture the effects of varying MPL surface morphology on PEFC performance and can be used in the design of new, optimized CL|MPL interface morphologies.