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Title: Reliability of the spherical agglomerate models for catalyst layer in polymer electrolyte membrane fuel cells
Authors: Zhang, Xiaoxian
Ostadi, Hossein
Jiang, Kyle
Chen, Rui
Keywords: PEM fuel cells
Catalyst layer
FIB/SEM nanotomography
Agglomerate model
Microscopic modelling
Issue Date: 2014
Publisher: © Elsevier
Citation: ZHANG, X. ... et al., 2014. Reliability of the spherical agglomerate models for catalyst layer in polymer electrolyte membrane fuel cells. Electrochimica Acta, 133, pp.475-483.
Abstract: The spherical agglomerate model with a single diameter is a common approach to describe the average electrochemical reaction rate in the catalyst layer of PEM fuel cells. Real agglomerates are highly irregular,and approximating them by independent spheres could give rise to errors. In this paper, we investi-gated these errors using nanotomography and numerical simulations. Three-dimensional microstructure of a cathode catalyst layer was acquired using FIB/SEM nanotomography, and oxygen diffusion andthe associated electrochemical reaction in the microstructure were simulated using pore-scale mod-elling. The simulated concentration and reaction rates at the pore scale were volumetrically averagedto obtain the average reaction rates. These simulated average reaction rates were then compared withthe results predicted by the spherical agglomerate model using an average diameter estimated from the 3D microstructure. The comparisons revealed that the spherical agglomerate model substantially over-estimated the reaction rates when the overpotential is high because of its incorrect description of the contact areas between the agglomerates and the macropores through which the oxygen diffuses. We also fitted the spherical agglomerate model to the simulated reaction rates by treating its diameter as a fitting parameter. The results showed that the value of the diameter needs to increase with the overpotential in order to match the simulated data. These findings implicate that the spherical agglomerate model needs to be used with care in catalyst layer design as its diameter is just a fitting parameter rather than a geometrical description of the agglomerates.
Description: NOTICE: this is the author’s version of a work that was accepted for publication in Electrochimica Acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.electacta.2014.04.060
Sponsor: This research was supported by the UK Technology Strategy Board (TSB Project No. TP/6/S/K3032H).
Version: Accepted for publication
DOI: 10.1016/j.electacta.2014.04.060
URI: https://dspace.lboro.ac.uk/2134/15616
Publisher Link: http://dx.doi.org/10.1016/j.electacta.2014.04.060
ISSN: 0013-4686
Appears in Collections:Published Articles (Aeronautical and Automotive Engineering)

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