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Surface Defect-mediated Reactivity of Au/TiO2(110)

Published online by Cambridge University Press:  15 February 2011

Ken T. Park ,
Minghu Pan ,
Vincent Meunier ,
William Shelton ,
Sergei Kalinin ,
Arthur P. Baddorf  and
E.W. Plummer
Ken T. Park
Affiliation:
Department of Physics and Astronomy, The University of Tennessee Knoxville, TN 37996, U.S.A. Department of Physics, Baylor University Waco, TX 76798, U.S.A.
Minghu Pan
Affiliation:
Department of Physics and Astronomy, The University of Tennessee Knoxville, TN 37996, U.S.A.
Vincent Meunier
Affiliation:
Computer Science and Mathematics Division, Oak Ridge National Laboratory Oak Ridge, TN 37831, U.S.A.
William Shelton
Affiliation:
Computer Science and Mathematics Division, Oak Ridge National Laboratory Oak Ridge, TN 37831, U.S.A.
Sergei Kalinin
Affiliation:
Condensed Matter Sciences Division, Oak Ridge National Laboratory Oak Ridge, TN 37831, U.S.A.
Arthur P. Baddorf
Affiliation:
Condensed Matter Sciences Division, Oak Ridge National Laboratory Oak Ridge, TN 37831, U.S.A.
E.W. Plummer
Affiliation:
Department of Physics and Astronomy, The University of Tennessee Knoxville, TN 37996, U.S.A. Condensed Matter Sciences Division, Oak Ridge National Laboratory Oak Ridge, TN 37831, U.S.A.
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Abstract

Metal clusters supported by transition metal oxides, as exemplified by the Au/TiO2 system, have found broad applications as catalytic and sensor materials. The unusual properties of these systems originate from the specific interactions of metal clusters mediated by an oxide substrate, including local reduction below the cluster. In this work, we present recent results on the local interactions between one-dimensional defects on a TiO2 surface and their reactivity with oxygen and Au nano-clusters studied by a combination of Scanning Tunneling Microscopy and Spectroscopy (STM/S). High-resolution STM images, interpreted with first-principles theory, show that the observed one-dimensional strands have partially reduced Ti atoms coordinated above three-coordinated, surface oxygen atoms. When strands are exposed to 5 x 10-7 Torr O2 at 300 K, oxygen is adsorbed and randomly nucleated on and along the strands. The results indicate the presence of exposed Ti that act as an active site for oxygen adsorption even at room temperature. Gold nano-particles of diameters 5 nm and less have also been deposited on the sub-stoichiometric rows of TiOx and characterized by STM. Like point defects and step edges on TiO2(110), the strands serve as nucleation sites for gold nano-clusters. The 1D defects of the surface are interpreted in terms of a surface crystallographic shear type structure, in contrast to the proposed Ti2O3 added row model by Onish and Iwasawa [Phys. Rev. Lett. 76, (1996) 791]. The implications of this behavior and specific interaction between gold clusters, defects and gas molecules for catalytic activity of the Au/TiO2 system are discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 876: Symposium A – Nanoporous and Nanostructured Materials for Catalysis, Sensor and Gas Separation Applications , 2005 , R4.6
Copyright
Copyright © Materials Research Society 2005

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