AVS 58th Annual International Symposium and Exhibition
    Surface Science Division Tuesday Sessions
       Session SS-TuP

Paper SS-TuP28
Deviation from Wulff Structures for Pt Nanoparticles Supported on TiO2(110): A STM Study

Tuesday, November 1, 2011, 6:00 pm, Room East Exhibit Hall

Session: Surface Science Poster Session
Presenter: Farzad Behafarid, University of Central Florida
Authors: F. Behafarid, University of Central Florida
B. Roldan Cuenya, University of Central Florida
Correspondent: Click to Email
This study reports the shape of micellar platinum nanoparticles (NPs) supported on TiO2(110) resolved by scanning tunneling microscopy (STM). Since micellar NPs are initially spherical in shape at room temperature, the 3D faceted shapes obtained after high temperature annealing display structures typical of thermodynamic equilibrium, in contrast with kinetic shapes of physical vapor deposited NPs, which are normally 2D and dominated by the diffusion of metal atoms on the support. All of the NPs resolved show an epitaxial relationship with the support, evident by TiO2(110)[001] direction being one of the symmetry axis of the NPs. Analyzing these shapes reveals that in addition to hexagonal top (type A) and square top (type B) NPs reported for evaporated NPs, there are two additional categories of shapes observed for micellar NPs (Type C and D). Type A and B consist only of 111 and 100 facets at the interface with the support and the free top surface. However, type C and D feature also 110 facets either at the interface with the support or at the free surface. This facet orientation was not observed before in other studies due to its instability and high surface energy. The ratio of 100/111 facets obtained for these shape deviates from the Wulff structure. This deviation could be attributed to size effects, interface-induced strain, and/or possible TiOx adsorbates on exposed facets.