Interpretation of Electrochemical Impedance Spectroscopy Using a Macrohomogeneous PEMFC Model

We have produced a transient, two-phase, non-isothermal model of the proton exchange membrane fuel cell (PEMFC), which can be used to directly simulate electrochemical impedance spectroscopy (EIS). For interpretation of EIS experiments, physics-based models offer several advantages over equivalent electrical circuit models. Equivalent circuit models require prior assumptions about the dominant processes contributing to impedance, and the relationship between physical and circuit parameters can be difficult to derive. In the physics-based model, all processes contribute to the impedance response, but the dominate process is easily determined. As an example, the PEMFC model reproduces an experimentally observed inductive loop at low frequencies. From the physics-based model, the inductive loop can be assigned to the modulation of membrane conductivity by product water generation. The EIS simulation technique can be applied to any transient electrochemical model without explicitly deriving the small signal response and without the assumption of linearity.