Mesoscale simulations of confined Nafion thin films.
Publication Date
2017-12Journal Title
The Journal of chemical physics
ISSN
0021-9606
Publisher
AIP
Volume
147
Issue
21
Pages
214904
Language
eng
Type
Article
This Version
AM
Physical Medium
Print
Metadata
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Vanya, P., Sharman, J., & Elliott, J. (2017). Mesoscale simulations of confined Nafion thin films.. The Journal of chemical physics, 147 (21), 214904. https://doi.org/10.1063/1.4996695
Abstract
The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains with carbon and quartz as confining materials for a wide range of operational water contents and
film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz
results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending of the confining material. The percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.
Sponsorship
EPSRC (1505322)
Identifiers
External DOI: https://doi.org/10.1063/1.4996695
This record's URL: https://www.repository.cam.ac.uk/handle/1810/271846
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