Analytical Impedance of PEM Fuel Cell Cathode Including Oxygen Transport in the Channel, Gas Diffusion, and Catalyst Layers

Abstract

A model for impedance of a PEM fuel cell cathode taking into account oxygen transport in the cathode catalyst layer (CCL), gas–diffusion layer (GDL) and in channel is solved analytically. A formula for the cathode impedance is valid for the cell current densities below 100 mA cm−2 and air flow stoichiometries exceeding 10. Least–squares fitting of experimental spectrum using the analytical result takes about 5 s on a standard PC. Fitting returns Tafel slope of the oxygen reduction reaction, double layer capacitance, CCL proton conductivity and oxygen diffusivities of the CCL and GDL. Analytical impedance can be coded as a user–defined function for a standard spectra fitting software supplied with EIS–meters.