Polymer-electrolyte fuel cells (PEFCs) provide multisector decarbonization solutions including in transportation, manufacturing, and long-term energy storage. They have become increasingly popular in these areas due to their high efficiency, power density, and low (or zero) emissions compared to traditional fossil-fuel dependent processes. The PEFC catalyst layer is the most complex and key part of the cell, and is critical for optimizing PEFC performance. Several studies have explored the structure/function relationships of PEFC catalyst layers, yet the physics and interactions controlling its in-situ formation remain a mystery. PEFC catalyst layers are traditionally fabricated out of a catalyst supported on a carbon nanoparticle with an ionomer, traditionally perfluorosulfonic acids (PFSAs) such as Nafion, as a binder, which stabilizes the carbon suspensions in the ink dispersion. Recent studies demonstrated the importance of pH as an experimental parameter for both comparison and characterization of such systems.¹

In this talk, we explore the interactions in the colloidal inks through detailed mathematical modeling. We propose a kinetics-based model representing species aggregation with pointwise interacting spheres that vary in charge through buried side chains for predicting the aggregation behavior of Nafion and carbon in solutions under varying conditions, such as solvent, Nafion wt% and carbon wt%. To demonstrate the accuracy and robustness of the model, we compare the results against a range of pH conditions and size distributions. The insights from the model help establish design criteria and guide future ink and process conditions.

Acknowledgements

This study was conducted under the Million Miles Fuel Cell Truck Consortium (M2FCT) funded by the Hydrogen and Fuel Cell Technologies Office in the Energy Efficiency and Renewable Energy Office of the U.S. Department of Energy under contract DE-AC02-05CH11231.

References

1. S. A. Berlinger, B. D. McCloskey, and A. Z. Weber, J. Phys. Chem. B, 122, 7790–7796 (2018).