Low-frequency EIS intercept as a diagnostic tool for PEM fuel cells degradation

Several diagnostic tests, such as polarization curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), were conducted periodically to monitor performance degradation during an accelerated stress test (AST) for catalyst degradation on a single proton exchange membrane (PEM) fuel cell, which involves voltage cycling. From the results of the EIS measurements taken during the AST at three different current densities, catalyst degradation is clearly shown. The lowfrequency intercept (Total R) increased most significantly. The simulation results with an 11-element impedance model show very good agreement with experimental data and consistency with the polarization change curves and CV. The obtained impedance at Total R is purely real, and it can be a useful and perhaps sufficient indicator for catalyst degradation and determination of the cell current state from just one parameter value, which is very promising for the future implementation in the PEM fuel cell control system