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Agglomerates in Polymer Electrolyte Fuel Cell Electrodes: Part I. Structural Characterization

Journal Article · · Journal of the Electrochemical Society
DOI:https://doi.org/10.1149/2.0571813jes· OSTI ID:1477745
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This two-part study characterizes the structural and transport properties of polymer electrolyte fuel cell (PEFC) cathode catalyst electrode. The agglomerates comprising the electrode are characterized with nano scale resolution X-ray computed tomography (nano-CT). A hybrid reconstruction technique is used to further refine the 3-D agglomerate microstructure and obtain 1-nm voxel resolution of the constituent catalyst, ionomer, carbon support and primary and secondary pore phases. Our analysis of nano-CT data shows that the electrode composition is heterogeneous and the agglomerates have structural heterogeneities in terms of size and composition. There is a strong correlation between the ionomer to carbon weight ratio (I/C) and agglomerate microstructure, suggesting that ionomer plays role in formation of larger agglomerates. With the hybrid reconstructions, we show that ionomer film thickness is spatially non-uniform inside the agglomerate and is strongly dependent on the I/C. Smaller agglomerate size and high I/C are shown to favor the ionomer impregnation. We demonstrate that the majority of the primary pores are smaller than 15 nm for I/C = 0.8 and higher I/C reduces the primary pore size. We also characterize the uniformity of the catalyst distribution and show that the majority of the catalyst is located away from the agglomerate surface.

Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
DOE Contract Number:
AC02-06CH11357
OSTI ID:
1477745
Journal Information:
Journal of the Electrochemical Society, Vol. 165, Issue 13; ISSN 0013-4651
Publisher:
The Electrochemical Society
Country of Publication:
United States
Language:
English

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Related Subjects

PEFC
PEMFC
agglomerate
catalyst Layer
electrode
ionomer film thickness
primary pore size