Heterogeneities of Aging within a PEMFC MEA

In this study, we investigated the long-term morphological and chemical changes of PEMFC cathode materials, with a special focus on the homogeneity of aging in different operating conditions (stationary or intermittent). The spatially-resolved physico-chemical analyses, performed at the cathode inlet/outlet region of the membrane electrode assembly, put in evidence that the cathode inlet ages much more rapidly than the cathode outlet in counter-flow mode, this effect being exacerbated at high cell current. The rationale for such observation is the existence of heterogeneities of local current density, essentially caused by the depletion in air partial pressure and the increase in water content along the gas-channel. We also evidenced heterogeneities of aging through the catalytic layer (CL). These heterogeneities are explained by the fact that Ptz+ ions produced by the corrosion of the PtCo/C nanoparticles are evacuated by the produced water exiting the CL [at the gas-diffusion layer (GDL)|CL interface] or consumed by H2 crossing-over from the anode through the cathode [at the CL|proton-exchange membrane (PEM) interface], resulting in the formation of the so-called platinum-band in the PEM.