AVS 52nd International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThA

Paper SS1-ThA9
Sintering of Au Clusters Supported on TiO@sub 2@(110): An In-Situ Scanning Tunneling Microscopic Study

Thursday, November 3, 2005, 4:40 pm, Room 202

Session: Transport and Structural Stabilization of Surfaces
Presenter: F. Yang, Texas A&M University
Authors: F. Yang, Texas A&M University
A. Kolmakov, University of California at Santa Barbara
A.K. Santra, Halliburton Company
D.W. Goodman, Texas A&M University
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Sintering, i.e. an increase in the average size of nanoclusters, is a frequently encountered problem in nanotechnology and a principle cause of deactivation in nanocatalysts. For example, Au supported on high-surface-area titania is a highly efficient catalyst for selective oxidation and hydrogenation reactions; however, commercial development is seriously hampered because Au nanoclusters sinter rapidly. The mechanisms of sintering are not well understood and depend, to a large extent, on understanding elementary surface diffusion processes. Scanning tunneling microscopy (STM) is capable of atomic-level measurements over a variety of conditions. In-situ STM allows the morphological changes of specific nanoclusters to be monitored over a variety of reaction conditions from ultrahigh vacuum to realistic reactant pressures. Using in-situ STM, the growth kinetics of Au on TiO@sub 2@(110) have been measured directly, allowing sintering mechanisms to be proposed for supported Au model catalysts under realistic reaction conditions. The STM results also show that substrate hydroxylation blocks the preferential growth of Au clusters and alters their growth kinetics on a TiO@sub 2@(110) surface. Furthermore, the sintering kinetics of Au clusters during the CO oxidation reaction have been studied for Au clusters supported on TiO@sub 2@(110) and on hydroxylated TiO@sub 2@(110).