Error Analysis of the Impedance Response of PEM Fuel Cells

A measurement-model-based error structure analysis was applied to impedance data collected under galvanostatic modulation for a single 5 cm2 polymer electrolyte membrane PEM fuel cell. The stochastic errors were found to be roughly independent of frequency and were similar for the two instruments used. The measurement-model approach was found to be capable of identifying both high-frequency and low-frequency artifacts in the spectra. The low-frequency inductive loops were found, in some cases, to be consistent with the Kramer–Kronig relations. In other cases, nonstationary phenomena were found to have influenced the low-frequency response. This work showed that once steady-state operation was achieved, the low-frequency inductive loops in the impedance response could be associated with physical phenomena within the fuel cell. In addition, the formalism of the measurement-model error analysis provides a means for determining whether a steady state has been achieved. © 2007 The Electrochemical Society. DOI: 10.1149/1.2747533 All rights reserved.