PEM fuel cell distribution of relaxation times: a method for the calculation and behavior of an oxygen transport peak
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Updated: Dec 11, 2025

A Guide to Concentration Alternating Frequency Response Analysis of Fuel Cells
Published on: December 11, 2019
1Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, IEK-14: Electrochemical Process Engineering, D-52425 Jülich, Germany. a.kulikovsky@fz-juelich.de and Lomonosov Moscow State University, Research Computing Center, 119991 Moscow, Russia.
Abstract:
A simple numerical method for the calculation of the distribution of relaxation times (DRT) for PEM fuel cell impedance is developed. The method combines the Tikhonov regularization technique and projected gradient iterations. The method is illustrated by calculating DRT for the synthetic impedance of two parallel RC-circuits and for Warburg finite-length impedance. Finally, cathode catalyst layer (CCL) impedance is calculated using the exact analytical solution and the method discussed is applied to understand the behavior of the DRT peak due to oxygen transport in the CCL. The position of the oxygen transport peak on the frequency scale exhibits non-monotonic behavior as the oxygen diffusion coefficient in the CCL decreases, which may serve as an indicator of CCL flooding. The Python code for DRT calculation is available for download.
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