Influence of ionomer content on the structure and performance of PEFC membrane electrode assemblies

Jian Xie, Fan Xu, David L. Wood, Karren L. More, Thomas A. Zawodzinski, Wayne H. Smith

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    118 Scopus citations

    Abstract

    Nafion® ionomer content of the cathode catalyst-layer of a polymer electrolyte fuel cell (PEFC), made by the "decal" hot pressing method, has been investigated for its effect on performance and structure of the membrane electrode assembly (MEA). Varying Nafion® content was shown to have an effect on performance within the entire range of polarization curves (i.e. kinetic, ohmic, and mass-transport regions) as well as on the structure. AFM analysis shows the effect of Nafion on the dispersion of carbon aggregates. Further analysis using TEM demonstrates the effect of Nafion on both the dispersion of carbon aggregates and the distribution and thickness of the Nafion ionomer films surrounding the catalyst/carbon aggregates. The MEA structure change correlates well with the MEA performance on both kinetics and mass-transport region. The determining factors on the performance of MEA are the interfacial zone (between the ionomer and catalyst particle), the dispersion of catalyst/carbon aggregates and the distribution/thickness of Nafion films. An optimized Nafion® content in the range of 27 ± 6 wt.% for the cathode was determined for an E-TEK 20% Pt3Cr/C catalyst at a loading of 0.20 mg Pt/cm2.

    Original languageEnglish
    Pages (from-to)7404-7412
    Number of pages9
    JournalElectrochimica Acta
    Volume55
    Issue number24
    DOIs
    StatePublished - Oct 1 2010

    Funding

    This work was supported by the U.S. Department of Energy, Office of Hydrogen, Fuel Cells & Infrastructure Technology and Office of Basic Energy Sciences−Chemical Sciences . Further acknowledgement is given to Jerzy Clistofor, Francisco Uribe, and Mahlon Wilson for helpful discussions.

    Keywords

    • Catalyst-layer structure
    • Ionomer content
    • MEA
    • Membrane electrode assembly
    • PEFC
    • Polymer electrolyte fuel cell

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