Small-angle neutron scattering studies on the distribution of polytetrafluoroethylene within microporous layers for polymer electrolyte fuel cells

• Published in: Composites. Part C, Open access Vol. 2; p. 100015
• Main Authors: Yoshimune, Wataru, Harada, Masashi, Akimoto, Yusuke
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-10-2020; Elsevier
• Subjects: Polymer electrolyte fuel cell; Polytetrafluoroethylene; Small-angle neutron scattering; Polytetrafluoroethylene; Polymer electrolyte fuel cell; Small-angle neutron scattering
• ISSN: 2666-6820; 2666-6820
• DOI: 10.1016/j.jcomc.2020.100015

•Contrast-variation small-angle neutron scattering was applied to elucidate studied the distribution of polytetrafluoroethylene within microporous layers for polymer electrolyte fuel cells.•A reduction of polytetrafluoroethylene self-aggregates within microporous layers was achieved by performing post-annealing above the PTFE melting point.•Better mass-transport properties under a high humidity cell condition were achieved when there were fewer PTFE self-aggregations within the microporous layers.
The performance of polymer electrolyte fuel cells depends on the nanostructure of the polymer composites in their components. The microporous layer within the cells, which generally comprises a composite of carbon black and polytetrafluoroethylene (PTFE), is a key component that prevents mass-transport losses in electrochemical reactions of the cells; therefore, we studied the distribution of PTFE within microporous layers using contrast-variation small-angle neutron scattering. By performing annealing above the PTFE melting point, its self-aggregations were reduced, and this effect was explained via the surface energies of PTFE and carbon black. Moreover, fuel cell performance testing demonstrated that better mass-transport properties were achieved when there were fewer PTFE self-aggregations within the microporous layers. Our findings suggest that an optimal PTFE distribution within fuel cell microporous layers can be achieved by engineering the surface energies of carbon black.