Platinum Stability at the Cathode of an Anion Exchange Membrane Fuel Cell

The determination of catalyst stability is as important as the determination of catalyst activity but receives much less attention because of the time required for measurement. Accelerated potential cycling tests do not always reflect the conditions experienced by catalysts operating in a fuel cell environment. Pt cathode electrodes operating at high steady-state potentials (0.8–1 V) in proton exchange membrane fuel cells (PEMFCs) have been reported to degrade due to Pt migration. Whether this phenomenon also occurs in anion exchange membrane fuel cells (AEMFCs) is not clear. In this study, an AEMFC with a Pt on Vulcan® carbon (Pt/C) cathode electrode was operated at 0.9 V steady-state potential for 1500 h. The electrode activity measured using an in situ reference electrode was found to decrease with time. Two significant changes in the Pt catalyst were found; the first was that the finely dispersed Pt catalyst agglomerated on the carbon substrate to form large clusters. The second change was that Pt was found in the polymer membrane structure. The results show that AEMFCs have similar stability concerns as PEMFCs regarding Pt catalyst material at cathodes electrodes.