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.

Probing water distribution in compressed fuel-cell gas-diffusion layers using X-ray computed tomography

“…For compressed GDLs, liquid water takes the higher-porosity transport pathways, thus implying that GDL architectures with modulated regions of high and low porosity could be used to control water removal, where the porosity difference has to be at least 0.1. The findings are consistent with recent studies of morphologically modified GDLs where milled or laser-perforated holes and lines serve as water-transport pathways [24][25][26][27][28][29], although these modifications were~100 μm, much larger than they needed to be based on the current study. However, evaporation/condensation due to thermal gradients and convection along the channel are not captured here but can have a significant impact on water distribution as in-operando studies for uncompressed GDLs have shown [30,31].…”

Understanding Water Transport in Polymer Electrolyte Fuel Cells Using Coupled Continuum and Pore‐Network Models

“…Continuum models use a volume averaged approach to model two-phase water transport coupled with electrochemistry [10][11][12]. These models allow for complex phenomena to be accounted for when describing water transport through GDL morphologies, where effective porous-domain properties are used (e.g., water-retention curves and Darcy's law) [13][14][15]; however, microstructural information in these models is coarse grained.…”

“…Herein, the advantage of both techniques is realized in an iterative scheme that utilizes well established continuum [10] and PN [24] models.…”

Investigating Evaporation in Gas Diffusion Layers for Fuel Cells with X-ray Computed Tomography

“…1 Thus, the heat transported with PCI flow is significant and needs a detailed investigation. Although water transport in GDLs has been investigated with modeling and experiments, [12][13][14][15] evaporation kinetics and PCI flow are poorly understood, primarily due to a lack of fundamental insight caused by the challenge of experimental measurements and visualization of the evaporating water front and distribution within these porous materials.…”