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

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 H-2/N-2 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. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.