Invited) Total Harmonic Distortion for PEM Fuel Cell

Electrochemical Impedance Spectroscopy (EIS) is well developed and widely applied for the study of electrode/electrolyte interfaces, films, coatings, and ion-transport mechanisms, among others. Measurement and analysis of traditional EIS is based on linear response in voltage or current to a sinusoidal perturbation. Small perturbations with linear responses are used in traditional EIS. Larger perturbations applied to nonlinear systems require a new set of tools. In the present study, we focus on the larger amplitude modulation and analysis of the harmonic response with the purpose of improving signal-to-noise ratio, and deriving additional information about the electrochemical system. Traditional EIS is extended to include Total Harmonic Distortion (THD) analysis. Non-linear harmonic distortion, instrument noise, and perturbation amplitude effects are discussed relative to monitoring oxygen concentration and operation status of a PEM fuel cell (PEMFC). Alternative approaches such as Intermodulation Distortion (IMD) are also introduced.