The Study of Surface Stability of Pt₃Co Alloys Under Oxygen Pressure Using AP-XPS and AP-STM

The Pt₃Co alloys has been the choice of catalyst for the proton-exchange membrane fuel cell due to significantly higher oxygen reduction rate (ORR) than pure Pt catalyst. While the Pt₃Co catalyst received much attentions for its excellent performance and extensive lifetime in fuel cell applications, the basic questions such as the role of Co in ORR and the chemical active states of Co elements, have not been clearly answered. To address the basic knowledges on these aspects, the study on a model system is highly necessary.<br/><br/>In this presentation, utilizing both ambient pressure X-ray photoelectron spectroscopy and scanning tunneling microscopy, our investigation on the surface chemical states and surface morphology of Pt₃Co (111) single crystal will be presented. Under the elevated oxygen pressure and temperature, the presence of surface segregation of transition metals is clearly observed. However, the surface morphology and chemial states in Pt₃Co are slightly different from those of Pt₃Ni alloy. To identify the chemically active site on surface, the reactivity of the nanostructured oxides and Pt is tested under CO oxidation condition, revealing important information on the role of interfacial oxygen on the nanostructured metal oxides.