Pore-Network Modeling of Water and Vapor Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

Lucas Van Oosterhout,Chao-Zhong Qin,S Hassanizadeh

doi:10.3390/computation4020021

Abstract

In the cathode side of a polymer electrolyte fuel cell (PEFC), a micro porous layer (MPL) added between the catalyst layer (CL) and the gas diffusion layer (GDL) plays an important role in water management. In this work, by using both quasi-static and dynamic pore-network models, water and vapor transport in the MPL and GDL has been investigated. We illustrated how the MPL improved water management in the cathode. Furthermore, it was found that dynamic liquid water transport in the GDL was very sensitive to the built-up thermal gradient along the through-plane direction. Thus, we may control water vapor condensation only along GDL-land interfaces by properly adjusting the GDL thermal conductivity. Our numerical results can provide guidelines for optimizing GDL pore structures for good water management.

Highlights

Water management plays a critical role in the performance and durability of low-temperature polymer electrolyte fuel cells (PEFCs)
We used the quasi-static pore-network modeling to illustrate the mechanism of the micro porous layer (MPL) in reducing liquid water coverage on the catalyst layer (CL) surface
We considered the condition of severe liquid water flooding in the cathode

Summary

Introduction

Water management plays a critical role in the performance and durability of low-temperature polymer electrolyte fuel cells (PEFCs). Compared to the anode side, water transport in the cathode has usually attracted more attention. It was found that in the cathode adding one/multiply micro porous layers (MPLs) between the catalyst layer (CL) and the GDL can dramatically improve the cell performance at high current densities. This improvement was primarily attributed to a better water management [6]. The MPL is typically consisted of carbon power bound with a hydrophobic polymer (e.g., PTFE) It has much smaller pore sizes than those in the GDL. Besides assisting in water management, the MPL performs several other roles in improving the GDL function such as providing a smooth surface in contact with the CL, preventing catalyst migration into the GDL substrate and losing contact with the membrane, and enhancing electronic transport to the bipolar plates [7]

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