|Title:||AC impedance modelling study on porous electrodes of proton exchange membrane fuel cells using an agglomerate model|
|Authors :||Gerteisen, Dietmar|
|Published in :||Journal of power sources|
|Publisher / Ed. Institution :||Elsevier|
|License (according to publishing contract) :||Licence according to publishing contract|
|Type of review:||Peer review (Publication)|
|Subjects :||Fuel cell; Ac impedance; Proton exchange membrane; Numerical model|
|Subject (DDC) :||621.3: Electrical engineering and electronics|
|Abstract:||A one-dimensional model of the PEM fuel cell cathode is developed to analyse AC impedance spectra and polarisation curves. The porous gas diffusion electrode is assumed to consist of a network of dispersed catalyst (Pt/C) forming spherically shaped agglomerated zones that are filled with electrolyte. The coupled differential equation system describes: ternary gas diffusion in the backing (O2, N2, water vapour), Fickian diffusion and Tafel kinetics for the oxygen reduction reaction (ORR) inside the agglomerates, proton migration with ohmic losses and double-layer charging in the electrode. Measurements are made of a temperature-controlled fuel cell with a geometric area of 1.4×1.4 cm^2. Lateral homogeneity is ensured by using a high air stoichiometry of 12. The experimentally observed doubling of the Tafel slope is reproduced by the model due to diffusion limitation inside the agglomerates. The model also predicts the behaviour of measured impedance spectra. Model parameters e.g. Tafel slope, ionic resistance and agglomerate radius are varied. It is found that the density of the active agglomerates changes due to the humidification of the electrode and that the Tafel slope changes according to a change in the ORR mechanism. A sensitivity analysis of the model parameters is conducted.|
|Departement:||School of Engineering|
|Organisational Unit:||Institute of Computational Physics (ICP)|
|Publication type:||Article in scientific Journal|
|Appears in Collections:||Publikationen School of Engineering|
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