Defects in Membrane Electrode Assembly Environments: An Approach to Understanding Membrane Degradation Processes
Authors: Pena-Duarte Armando , Quesada Calita Maria , Wang Xiaojing , Leonard Daniel P , Borup Rod L. 
Published: December 2024

The performance and long-term durability of polymer electrolyte membrane fuel cells (PEMFCs) are subject to different factors ––material properties, defects, assembly, maintenance and operational procedures.1 Among all the possible failure modes in a fuel cell, membrane electrode assembly (MEA) degradation is a determining factor for performance and lifetime.2 In the past few years, several studies have been developed to understand the degradation of membranes and electrocatalysts, and the corrosion of the carbon support; with a focus on the chemical aspects, rather than the physical features that could promote degradation. More studies are needed to evaluate physical factors that can compromise the MEA structure, especially the aspects that affect the membrane.3 The physical degradation of membranes can be effected by membrane intrinsic factors such as membrane creep, microcracks, and morphological changes.4

Furthermore, it is necessary to study the influence of membrane extrinsic factors ––such as roughness and imperfections at the interfaces between MEA components–– on the processes of membrane degradation. Whether morphological defects are generated before or during the assembly procedure or are intentionally introduced as strategy to improved water management, remains unclear if a defect can act as a precursor pit where membrane could start its degradation. In this sense, more efforts are needed to evaluate the influence of defects on potential and progressive membrane etching and pinholes formation.
Our work is focused on understanding the influence of defects, specifically cracks present on gas diffusion layers (GDLs), on the performance and durability of PEMFCs. To control experimental variables associated with different production lots and suppliers, we designed a method to create artificial cracks on the mesoporous layers (MPLs) of commercial GDLs. This technique allows us to compare the cracked GDLs with the pristine GDL, ensuring our “network or pattern of cracks” as the only external variable introduced into the MEA environment. Also, we utilized other commercially available intentionally cracked GDLs as comparative elements. Accelerated stress test (ASTs) were performed and durability results were obtained from long-term (500 hours) fuel cell operation at elevated cell temperature (90 oC). Scanning electron microscopy (SEM) and laser profilometry, were used to characterize all the samples, before and after performance/durability tests. Mechanical and chemical durability of membranes are evaluated based on fluoride emission rates (FERs).
This work enables a starting approach to understand the influence of cracks, existing on GDLs, on the membrane degradation processes. Results will give us insights for improving the membrane and GDLs technologies that we are developing in the Million Mile Fuel Cell Truck Consortium (M2FCT).
Acknowledgement:
This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos.
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