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

Invited Paper SS1-ThM3
Cluster Size and Support Effects on Activity in Supported Gold and Iridium Catalysts

Thursday, November 18, 2004, 9:00 am, Room 210B

Session: Metal Oxide and Clusters III: Supported Cluster Formation and Reactivity
Presenter: S.L. Anderson, University of Utah
Authors: S. Lee, University of Utah
C. Fan, University of Utah
T. Wu, University of Utah
W. Kaden, University of Utah
S.L. Anderson, University of Utah
Correspondent: Click to Email
Size-selected model catalysts are prepared by deposition of mass-selected gold and iridium cluster ions on single crystal TiO@sub 2@ and thin film Al@sub2@O@sub 3@. Physical properties and adsorbate binding to the resulting samples is probed by a combination of XPS and ion-scattering (ISS). Chemical activity is probed by a combination of temperature-programmed desorption and constant temperature pulse dosing mass spectrometry. CO oxidation on Au@sub n@/TiO@sub 2@ is found to be very strongly dependent on deposited cluster size, with activity turning on at Au@sub 3@, and varying with size for larger clusters. The activity appears to be correlated with changes in the binding of CO from atop gold to peripheral sites associated with the clusters. Comparison of samples prepared by deposition over a wide temperature range suggests that substantial sintering occurs only at temperatures well above room temperaure. Reactions of hydrazine and ammonia on Ir@sub n@/Al@sub2@O@sub 3@, and sintering behavior in this system will also be discussed.