PEM Fuel Cell Characterization by Means of the Physical Model for Impedance Spectra

A recent analytical solution of the physical model for the PEM fuel cell impedance [A. A. Kulikovsky, J. Electrochem. Soc. , 162 , F217 (2015)] is used for least–squares fitting of experimental impedance spectra. Ten spectra are collected in one experimental run of a cell with ten segments operated at a current density of 100 mA cm − 2 under high stoichiometry of the oxygen flow. The model impedance is fitted to the spectra and the resulting physical parameters of the cathode side are discussed. Of particular interest is a low value of the oxygen diffusion coefficient in the cathode catalyst layer ( ≃ 0.45 · 10 − 4 cm 2 s − 1 ), a parameter, which has not been measured in situ so far. This low value, as well as a high value of the cathode catalyst layer (CCL) proton conductivity σ p ≃ 0.054 Ω − 1 cm − 1 is attributed to a large amount of liquid water in the CCL.