Performance and Impedance of a Partially Flooded Cathode Catalyst Layer in a Low-Platinum Polymer Electrolyte Membrane Fuel Cell

A model for performance and impedance of a partially flooded cathode catalyst layer (CCL) in a low-platinum PEM fuel cell is developed. The CCL is modeled by a system of cylindrical pores approximating real pore-size distribution in the electrode. The model includes oxygen transport along the pores and through the ionomer film covering Pt/C agglomerates. Part of the pore domain adjacent to the membrane is allowed to be flooded. Fitting of the model to experimental impedance spectra of a low-platinum PEM fuel cell shows 30%-40% CCL flooding. Flooding effectively reduces the CCL volume available for current conversion, thereby lowering the limiting current density due to oxygen transport through the ionomer film.