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 (SOFC) membrane-electrode assembly (MEA) is developed and used as the basis for simulating electrochemical impedance spectra (EIS). The one-dimensional model includes porous-media transport, elementary heterogeneous chemical reaction, ion conduction, and electrochemical charge transfer. Porous-media 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.