Lawrence Berkeley National Laboratory

A mathematical framework for simulating the impedance response of a proton-exchange-membrane fuel cell (PEMFC) was developed to provide insight into the coupled physics and chemistry that influence observed spectra. The model was based on a cell-level continuum model that was linearized and represented in the frequency domain, which allowed for the accounting of coupled transport in a PEMFC and the simulation of full spectra in seconds. Good agreement was observed between experimental and simulated polarization and impedance data. Consistency between steady-state and frequency-domain continuum models was confirmed, which allowed for the extraction of kinetic information from the experimental impedance spectra. The model framework was used to estimate contributions associated with ohmic, charge-transfer, and transport resistances, which was shown to align with power-loss voltage breakdown analyses of steady-state simulations. A proposed equivalent-circuit model facilitated estimates of the low-frequency impedance, which can be used in conjunction with the impedance model to assess properties of the electrochemical cell. Since the model accounted for the effects of coupled physics, pressure impedance transfer functions were simulated, which showed quantitative agreement with experimental observations from literature.