Influence of wettability on liquid water transport in gas diffusion layer of proton exchange membrane fuel cells (PEMFC)

TL;DR

This study uses pore-scale simulations to analyze how wettability affects water transport in gas diffusion layers of PEMFCs, revealing significant changes in invasion patterns and saturation related to pore wettability, with implications for fuel cell design.

Contribution

It provides new insights into water invasion patterns in GDLs considering mixed wettability and suggests extensions to 3D systems for better fuel cell optimization.

Findings

Water invasion pattern shifts from fractal to compact with wettability change.

Saturation at breakthrough depends on the fraction of hydrophilic pores.

Results inform GDL design for improved water management and fuel cell performance.

Abstract

Water management is a key factor that limits PEFC's performance. We show how insights into this problem can be gained from pore-scale simulations of water invasion in a model fibrous medium. We explore the influence of contact angle on the water invasion pattern and water saturation at breakthrough and show that a dramatic change in the invasion pattern, from fractal to compact, occurs as the system changes from hydrophobic to hydrophilic. Then, we explore the case of a system of mixed wettability, i.e. containing both hydrophilic and hydrophobic pores. The saturation at breakthrough is studied as a function of the fraction of hydrophilic pores. The results are discussed in relation with the water management problem, the optimal design of a GDL and the fuel cell performance degradation mechanisms. We outline how the study could be extended to 3D systems, notably from binarised images of GDLs obtained by X ray microtomography.