Paper SS1+NC-TuA11
Stability, Electronic, and Catalytic Properties of Supported Metal Clusters

Tuesday, October 21, 2008, 5:00 pm, Room 208

The next generation of nanocatalysts requires detailed knowledge of the correlation between their structure and reactivity. Size- and shape-selected Au, Pt and AuFe nanoclusters with well defined intercluster distances were synthesized by diblock copolymer encapsulation. Significant changes in the electronic local density of states (LDOS) of TiC-supported Au clusters, in particular, the onset of non-metallic behavior, were observed by scanning tunneling spectroscopy with decreasing cluster size. In addition, evidence for substrate-induced modifications in the LDOS of interfacial gold atoms was found.¹ Our temperature programmed desorption (TPD) measurements indicated a size-dependency in the catalytic activity of Au/TiC for CO oxidation.² Furthermore, interparticle interactions were found to affect the activity and life-time of our catalysts.³ The stability of oxidized gold species formed upon cluster exposure to atomic oxygen was investigated using a combination of temperature-, time- and CO dosing-dependent X-ray photoelectron spectroscopy and TPD.⁴ Our work demonstrates the formation of surface and sub-surface Au₂O₃ on Au nanoparticles. Interestingly, the stability of these species upon thermal treatment was found to depend on the reducibility of the oxide support. Finally, the formation, surface reconstruction and high-temperature mobility of size-selected bimetallic AuFe⁵ and Pt nanoclusters deposited on TiO₂(110) will be presented.

¹A. Naitabdi, L. K. Ono, B. Roldan Cuenya, Appl. Phys. Lett. 89, 043101 (2006)
²L. K. Ono, D. Sudfeld, B. Roldan Cuenya, Surf. Sci. 600, 5041 (2006)
³L. K. Ono, B. Roldan Cuenya, Catal. Lett. 113, 86 (2007)
⁴L. K. Ono, B. Roldan Cuenya, J. Phys. Chem. C 112, 4676 (2008)
⁵A. Naitabdi, B. Roldan Cuenya, Appl. Phys. Lett. 91, 113110 (2007).