Electron and proton conductivity of Fe-N-C cathodes for PEM fuel cells: A model-based electrochemical impedance spectroscopy measurement

Impedance spectra of a PEM fuel cell with three Fe-N-C cathodes have been measured under the H-2/N-2 testing regime. The spectra have been fitted using a recently developed physics-based impedance model, which takes into account finite proton (sigma(p)) and electron (sigma(e)) conductivity of the oxygen-free cathode catalyst layer. Fitting allowed to extract numerical data for sigma(p), sigma(e), the double layer capacitance, and the inductance of cables used for measuring impedance spectra. The values of sigma(p) and sigma(e) are close to what previously found for standard Pt/C electrodes, which is found for the first time using PGM-free catalysts. The method enables simultaneous measurement of reference proton and electron conductivity of PEMFC cathode.