Distribution of Relaxation Times: A Tool for Measuring Oxygen Transport Resistivity of a Low–Pt PEM Fuel Cell Cathode

Abstract

Oxygen transport resistivity of the cathode catalyst layer in a low–Pt PEM fuel cell has been determined using two methods: the first one is fitting of our recent physics–based impedance model to the experimental impedance spectra of the cell, and the second is calculation of distribution of relaxation times (DRT) using the same spectra. Comparison of the two methods shows that the DRT peak with the characteristic frequency on the order of 500 to 1000 Hz describes oxygen transport in the open pore and in Nafion film covering Pt/C agglomerates in the catalyst layer. This result makes it possible using experimental impedance spectroscopy and DRT calculation for routine measurements of cathode transport resistivity in low–Pt PEMFCs.