Electrochemical Signatures in Proton Exchange Membrane Fuel Cells: A Comprehensive Study Based on Distribution of Relaxation Times

Abstract

The Distribution of Relaxation Times (DRT) method is increasingly applied to electrochemical impedance spectroscopy (EIS) for polymer electrolyte membrane fuel cells (PEMFCs), yet peak interpretation remains challenging due to overlapping processes and sensitivity to operating conditions. In this work, impedance spectra were measured on a well-defined single PEMFC across a broad experimental matrix, including variations in voltage, temperature, pressure, gas stoichiometry, and oxidant type. The novelty of this study lies not in the identification of peaks themselves, but in the systematic quantification of how their relative contributions evolve under such diverse conditions. A non-linear statistical framework was employed to reveal correlations between peaks and operating parameters, thereby elucidating the highly non-linear mechanistic interplay underlying PEMFC operation. This approach also enables assessment of the statistical significance of peaks, distinguishing genuine electrochemical features from phantom peaks, while the presentation of the average DRT reconstruction error with confidence intervals highlights non-negligible uncertainties in the high-frequency region. Dataset collected by Francesco Mazzeo during his research period abroad at the University of Chemistry and Technology Prague as part of his PhD program at Politecnico di Torino, carried out within the PNRR-NGEU project, which received funding from the MUR – DM 352/2022, as well as from Eaton.