A comparison of PEM fuel cell parameters resulting from the distribution of relaxation times, distribution of transport times, and physics-based modeling

Recently, the Distribution of Transport Times (DTT) technique has been suggested as a supplement to the distribution of relaxation times (DRT) technique for analyzing impedance spectra of PEM fuel cells. In this study, we compare the faradaic and transport resistivities obtained from DRT and DTT with those resulting from fitting the physics-based model (PBM) to the experimental spectra. The DTT of the PEMFC impedance without the low-frequency inductive loop yields peak resistivities that closely match those obtained from the PBM, whereas the peak resistivities derived from the DRT are generally less accurate. Moreover, unlike the DRT spectrum, the DTT successfully resolves the transport peak. We propose a modification to the composite kernel used in the DTT to describe spectra with a low-frequency “inductive” loop. An example of DTT calculated from an experimental spectrum containing such a loop is demonstrated.