Interactions between Catalyst Layer Degradation and Liquid Water Distribution in Polymer Electrolyte Fuel Cells
Authors: Aroge Fabusuyi Akindele , Halter Jonathan , Lowe Olivia C , MacDonald John A , Orfino Francesco P , Dutta Monica , Kjeang Erik 
Published: February 2024

Managing liquid water distribution in PEFCs is critical to desirable high power density operation and cell durability [1–3]. Degradation modes such as carbon corrosion in the cathode catalyst layer (CCL) are believed to depend on local humidification [2,4], while the distribution of liquid water may also be influenced by performance drop associated with such degradation [3]. Although some studies have shown the influence of carbon corrosion on liquid water distribution [2,3], the possible reverse effect of liquid water distribution on the CCL degradation requires further investigation.
The objective of the present work is to establish a deeper understanding of the cause-and-effect interactions between CCL degradation and liquid water distribution. This is achieved experimentally by carrying out voltage-cycling accelerated stress tests (ASTs) on fuel cells which differ only in the constituent gas diffusion layers (GDLs); namely, SGL 22 BB and a proprietary Avcarb. Three-dimensional X-ray microscopy is used to observe both degradation effects and liquid water distribution at different stages of the ASTs. A relatively rapid operando two-dimensional visualization technique [5] was also used to investigate the differences in liquid water distribution between the two GDLs. The fuel cells imaged are analyzed and exhibit different liquid water distributions, whereby the Avcarb exhibits a higher liquid water condensation close to the CCL, compared to the SGL. Supported by model results, this difference in liquid water distribution is shown to be attributable to the different transport properties of the GDLs. The degradation results, such as the CCL thickness (Fig. 1) show that the Avcarb cell experiences a faster CCL degradation than the SGL cell. Furthermore, the Avcarb liquid water distribution is seen to change with increasing AST cycles in a manner indicating higher vapour phase removal. These results provide insights for GDL design consideration, showing that GDL transport properties may influence liquid water distribution at the electrode with important implications for CCL durability.

Acknowledgement

Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada,
Ballard Power Systems, Canada Foundation for Innovation, British Columbia Knowledge Development Fund,
and Canada Research Chairs.

References

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Figure 1