Stability of platinum based alloy cathode catalysts in PEM fuel cells

Corrosion and surface area changes of platinum (Pt) based catalysts supported on carbon were evaluated using an accelerated durability test (ADT). The results obtained using the ADT were correlated to the performance of the Pt based catalysts in the fuel cell. The catalytic activity and dissolution rate of the alloying metal from the Pt-alloy catalysts were estimated in the same time domain. A strong correlation was observed between the amount of the alloying metal dissolved and the oxygen reduction reaction (ORR) activity of the Pt-alloy catalysts. The Pt catalyst exhibited loss of active surface area, and a resulting decrease in the ORR activity was observed. The Pt/C and Pt–Co/C catalysts showed similar behavior in both ADT and in the fuel cell testing. Cross-sectional studies by electron microprobe analysis of the membrane electrode assembly after fuel cell testing revealed cobalt dissolution followed by diffusion into the membrane.