Investigation of Stability Reduction in PtCoMn Ternary Alloy Catalyst for PEFCs

In this study, PtCoMn / High surface area carbon (HSAC) ternary alloy catalysts were evaluated stability against voltage cycling test in MEA. Oxygen reduction reaction (ORR) activity of PtCoMn catalyst decreased gradually in each test. The stability of PtCoMn / HSAC was not comparable to existing Pt and PtCo catalysts. To understand the mechanism of decreasing ORR activity of PtCoMn / HSAC, the MEA which was used in voltage cycling test was investigated by SEM / EDX mapping analysis and EPMA line analysis. As a result of the analysis, a lot of Pt particles were found at the interface of Nafion membrane and cathode catalyst, and Co and Mn elements were detected in the membrane. These results suggest that not only Pt but also Co and Mn in the PtCoMn catalyst dissolved and turn to be metal ions during the test. Then, Pt ions were re-deposited as Pt metal particles at the interface during the test. These results indicate that stability decrease of PtCoMn catalyst would be caused by the dissolution of the metal in the catalyst.