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 cm2 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 σp ≃ 0.054 Ω− 1 cm− 1 is attributed to a large amount of liquid water in the CCL.