Measurement of protonic resistance of catalyst layers as a tool for degradation monitoring

Abstract

The ionic resistance of a PEM fuel cell catalyst layer, as well as the double layer capacity and the high frequency resistance are estimated from the impedance spectra of H2/N2 operated cell, thanks to a volumetric electrode model. The impedance spectra are calculated in the case of a homogeneous distribution of resistivity and capacity, and considering both through plane and in plane heterogeneities.Then, results of the degradation of a MEA subjected to four different accelerated stress tests are presented. They consist of (i) a constant current operation, (ii) 1.2 V potential hold with nitrogen and hydrogen (iii) open circuit voltage (OCV) hold with air and hydrogen, and (iv) a start-up protocol where heterogeneous degradations are observed using a linear segmented fuel cell. This technique can provide useful information about the evolution of catalyst layer microstructure during AST.