Oxygen Transport Effects of Cobalt Cation Contamination of Ionomer Thin Films in Proton Exchange Membrane Fuel Cells

Abstract

This work was performed to experimentally characterize the oxygen transport resistance effects of cobalt contamination of the ionomer inside of polymer electrolyte membrane fuel cells (PEMFCs). We created a test cell capable of decoupling the ionomer from the membrane electrode assembly, allowing for independent bulk and thin-film ionomer testing using limiting current techniques. Three levels of cobalt-doped bulk ionomers were tested in this study, including un-doped, minimally-doped (5% exchange), and fully-doped cases. The results showed an increase in oxygen transport resistance, both with a decrease in sample relative humidity and an increase in cobalt doping. These results were consistent with hypotheses derived from previous studies of the water content and ionomer structure effects of cationic contamination of the ionomer in PEMFCs.