Influence of ionomer content on the structure and performance of PEFC membrane electrode assemblies |
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Authors: | Jian Xie Fan Xu Karren L. More Wayne H. Smith |
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Affiliation: | a Department of Mechanical Engineering, Purdue School of Engineering and Technology, Indiana University-Purdue University, 723 West Michigan Street, SL 260M, Indianapolis, IN 46202, United States b Electronic and Electrochemical Materials and Devices (MST-11) Group, Los Alamos National Laboratory, Los Alamos 87545, NM, United States c Corrosion Sciences and Technology Group, Oak Ridge National Laboratory, Oak Ridge 37831-6064, TN, United States d Department of Chemical Engineering, Case Western Reserve University, Cleveland 44106-7217, OH, United States |
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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. |
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Keywords: | Ionomer content Membrane electrode assembly MEA Catalyst-layer structure Polymer electrolyte fuel cell PEFC |
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