AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThM

Paper SS1-ThM9
Adsorption and Desorption of Propylene and Ethylene on Au/TiO@SUB 2@

Thursday, November 18, 2004, 11:00 am, Room 210B

Session: Metal Oxide and Clusters III: Supported Cluster Formation and Reactivity
Presenter: Y. Yang, University of California, Santa Barbara
Authors: Y. Yang, University of California, Santa Barbara
M.M. Sushchikh, University of California, Santa Barbara
E.W. McFarland, University of California, Santa Barbara
Correspondent: Click to Email
TiO@sub 2@ supported Au nanoclusters are of interest both as olefin epoxidation catalysts as well as a more general high activity partial oxidation platform. Four different TiO@sub 2@ (110) surfaces were prepared; ideal, fully oxidized, and defected by 0.1% , 1% and 10% surface area sputtering. Identical exposures (<1Å ) of Au were evaporated on each surface and the existence of Au verified by XPS. On the fully oxidized surface after exposure to propylene at 100 K, TPD of propylene shows a 150 K desorption peak from TiO@sub 2@ sites and a 210 K peak from Au/TiO@sub 2@ sites. The 150 K multilayer peak is the largest following large exposures, however, at low exposures the 210 K peak is occupied first. On the 1% and 10% sputtered surface, the Au/TiO@sub 2@ related peak 210 K peak shifts to higher temperature (210 K -> 270 K (1%) and 300 K (10%)) while the TiO@sub 2@ related peak remains at 150 K. We propose that Au deposited on a sputtered surface is immobilized at defect sites and that with increased sputtering time there is a decrease in the cluster size. The propylene metal interaction is increased in energy as the cluster size decreases. Similar behavior is observed with ethylene desorption.