Modeling Electrochemical Impedance Spectra in SOFC Button Cells with Internal Methane Reforming

A time-accurate transient model of an anode-supported solid-oxide-fuel-cell ͑SOFC͒ membrane-electrode assembly ͑MEA͒ is developed and used as the basis for simulating electrochemical impedance spectra ͑EIS͒.The one-dimensional model includes porous-media transport, elementary heterogeneous chemical reaction, ion conduction, and electrochemical charge transfer.Porousmedia transport is represented by the dusty-gas model and electrochemical charge-transfer is modeled with a modified Butler-Volmer formulation.A button-cell configuration is used, with the fuel and air flows modeled as perfectly stirred reactors.Impedance spectra are determined by imposing oscillating electric currents over a range of frequencies and observing the resulting cell voltage.Results are discussed for hydrogen and methane fuels, including the effects of internal methane reforming chemistry.