Title: Investigation of the cathode active layer of PEM fuel cells using AC impedance spectroscopy
Authors : Gerteisen, Dietmar
Hakenjos, Alexander
Schumacher, Jürgen
Proceedings: 2nd European PEFC Forum 2003. Proceedings. Vol.1 : 30 June - 4 July 2003, Lucerne, Switzerland
Volume(Issue) : 1
Pages : 271
Pages to: 282
Conference details: 2nd European Polymer Eletrolyte Fuel Cell (PEFC) Forum, Lucerne, 30 June - 4 July 2003
Publisher / Ed. Institution : European Fuel Cell Forum
Issue Date: 2003
License (according to publishing contract) : Licence according to publishing contract
Type of review: Editorial review
Language : English
Subjects : Pefc; Fuel cells; Ac impedance spectroscopy
Subject (DDC) : 621.3: Electrical engineering and electronics
Abstract: This paper presents the characterisation of the cathode electrode of proton exchange membrane (PEM) fuel cells by means of AC impedance spectroscopy. Measured steady-state voltammograms and impedance spectra are compared to simulation results obtained with two different models for the cathode electrode. A test fuel cell with an active area of 1.4x1.4 cm^2 and meander-shaped flow-fields is used for the measurements. The cell temperature can be controlled. Measured steadystate voltammograms in the region of low overpotential show a change in the Tafel slope. The radius of the measured AC impedance arc decreases with increasing overvoltage, shows a minimum value and subsequently grows again as the overpotential increases. This is interpreted as mass transport limitation of oxygen. Two mathematical models for the simulation of AC impedance spectra and polarisation curves are investigated. The multi-step model is based on two electrochemical steps for the oxygen reduction reaction (ORR) mechanism. A second model accounts for oxygen transport limitation in spherical agglomerates. It is assumed that in the catalyst layer the dispersed catalyst (Pt/C) forms agglomerated zones filled with the electrolyte. The measured polarisation curves can be fitted both by the multi-step model and the agglomerate model. The quantitative impedance values are reproduced by the multi-step model. However, it does not reproduce the oxygen transport limitation which is observed experimentally. This feature of the impedance spectra is captured by the agglomerate model.
Departement: School of Engineering
Organisational Unit: Institute of Computational Physics (ICP)
Publication type: Conference paper
ISBN: 3-905592-13-4
URI: https://digitalcollection.zhaw.ch/handle/11475/11810
Appears in Collections:Publikationen School of Engineering

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