The drive to reduce the Pt loading in the PEMFC cathode in order to minimize the overall Pt in the fuel cell system below 10-15 g Pt/vehicle requires a durable and stable catalyst that has desirable characteristics such as high activity and low oxygen and proton transport resistances. The carbon support plays an important role in determining the catalyst nanoparticle distribution and transport properties in the electrodes. Therefore, it is vital to understand the degradation mechanisms of both the Pt and carbon support to develop better PEMFC cathodes for automotive applications.

In this study, we evaluated the performance and morphological changes after voltage-cycling accelerated stability tests for Pt and PtCo catalysts supported on different carbon supports. Among the catalysts with different carbon supports, it was found that although the Pt surface area loss, strongly related to Pt dissolution, was comparable, the losses in oxygen reduction kinetics and fuel cell performance for catalysts with high-surface-area carbon were smaller. We studied and will report changes in electrochemical properties, Pt and Co redistribution, and electrode morphology. Simulation to illustrate the stability differences will also be discussed.

This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.