Liquid transport in gas diffusion layer of proton exchange membrane fuel cells: Effects of microporous layer cracks

Micro porous layer (MPL) is a carbon layer (similar to 15 mu m) that coated on the gas diffusion layer (GDL) to enhance the electrical conduction and membrane hydration of proton exchange membrane fuel cell (PEMFC). However, the liquid transport behavior from MPL to GDL and its impact on water management remain unclear. Thus, a three-dimensional volume of fluid (VOF) model is developed to investigate the effects of MPL crack properties on liquid water saturation, liquid pathway formation, and the two-phase mass transport mechanism in GDL. Firstly, a stochastic orientation method is used to reconstruct the fibrous structure of the GDL. After that, the liquid water saturation calculated from the numerical results agrees well with the experimental data. With considering the full morphology of the overlap between MPL and GDL, it's found that this overlap determines the preferred liquid emerging port of both MPL and GDL. Three crack design shapes in MPL are proposed on the base of the similarity crack formation processes of soil mud. In addition, the effects of crack shape, distance between cracks, and crack number on liquid water transport from MPL to GDL are investigated. It is found that the liquid water saturation of GDL increases with crack number and the distance between cracks, while presents little correlation to the crack shape. Hopefully, these results can help the development of PEMFC models without reconstructing full MPL morphology. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the effects of crack properties in the micro porous layer (MPL) on liquid water saturation, liquid pathway formation, and two-phase mass transport mechanism in proton exchange membrane fuel cells (PEMFC) using a three-dimensional volume of fluid (VOF) model. The results show that the overlap between MPL and gas diffusion layer (GDL) determines the preferred liquid emerging port, while the crack shape has little influence on the liquid water transport.