Paper SS1-WeM4
Pt Terminated Mono- and Multilayer CuPt Alloys Supported on Ru(0001) Single Crystals as Model System for Core Shell Particles

Wednesday, November 2, 2011, 9:00 am, Room 107

A popular concept to improve the catalytic activity of metal particles is the utilization of core shell particles. This means that a metal/alloy core is encapsulated by an additional metal in the shell of the particle. An interesting example has recently been published by R. Srivastava et al. [1], who found that Pt enclosed alloy particles containing Cu, Co and Pt, have a much better activity towards oxygen reduction than pure Pt. Whereas the principle concept is thus proven to work, the “optimum catalyst” for oxygen reduction has not yet been found.

For a better understanding of the structure and the formation of such core shell particles we prepare nanostructured planar model surfaces under well defined conditions, such as in ultra high vacuum (UHV). The surfaces consist of mono- and multilayer CuPt alloys on a Ru(0001) single crystal. They can be prepared by subsequent evaporation of the single metals and annealing at elevated temperatures. By this means the composition of the core can be well defined. The shell can be achieved by terminating the alloy by an additional Pt layer.

In this work we focus on the preparation of mono and bimetallic CuPt layers. They are characterized via STM to elucidate the morphology as well as the atom distribution. From the atom distribution within the alloy we will discuss the dominant factor for alloy formation, in view of the different size of the atoms and difference in their intermetallic bonding. Furthermore we will elucidate the surface segregation behavior of Pt in the bilayer alloy during the alloying process.