Hostname: page-component-586b7cd67f-t8hqh Total loading time: 0 Render date: 2024-11-28T16:50:31.304Z Has data issue: false hasContentIssue false
  • English
  • Français

Atomic and Electronic Structures of Nano-Interface In Au/TiO2 Catalyst - Electron Microscopic Approach -

Published online by Cambridge University Press:  11 February 2011

S. Ichikawa ,
K. Okazaki ,
T. Akita ,
M. Okumura ,
K. Tanaka  and
M. Kohyama
S. Ichikawa
Affiliation:
National Institute of Advanced Industrial Science and Technology (AIST Kansai), 1–8–31 Midorigaoka, Ikeda, Osaka, 563–8577, Japan
K. Okazaki
Affiliation:
National Institute of Advanced Industrial Science and Technology (AIST Kansai), 1–8–31 Midorigaoka, Ikeda, Osaka, 563–8577, Japan
T. Akita
Affiliation:
National Institute of Advanced Industrial Science and Technology (AIST Kansai), 1–8–31 Midorigaoka, Ikeda, Osaka, 563–8577, Japan
M. Okumura
Affiliation:
National Institute of Advanced Industrial Science and Technology (AIST Kansai), 1–8–31 Midorigaoka, Ikeda, Osaka, 563–8577, Japan
K. Tanaka
Affiliation:
National Institute of Advanced Industrial Science and Technology (AIST Kansai), 1–8–31 Midorigaoka, Ikeda, Osaka, 563–8577, Japan
M. Kohyama
Affiliation:
National Institute of Advanced Industrial Science and Technology (AIST Kansai), 1–8–31 Midorigaoka, Ikeda, Osaka, 563–8577, Japan
Get access

Abstract

The size dependence of the catalytic property of the gold catalysts has been reported. It is especially interesting that the catalytic property of gold suddenly changes to show a platinum-like behavior when the mean size of gold is below 2nm. This phenomenon should be owing to the change of the electronic structure of the gold, however its detail has not been cleared yet. We investigated the size dependence of the mean inner potential of gold catalysts supported on TiO2, which is affected by the outer valence electron, using electron holography and high-resolution electron microscopy. We found the following tendency. When the size of the gold particle is over 5nm, the values of the mean inner potential are the same level as the reported experimental values of the bulk gold (21–23V) and the calculated values of the bulk gold (25–30V). When the size is below 5nm, the mean inner potential begins to increase over 30V, and it begins to increase suddenly over 40V at the size below about 2nm. It indicates that the electronic structure of the gold particles varies from that of the bulk state as the size of the gold particles reduces. Due to the size reduction, the volume fraction of the surface atoms and the interface atoms increases, e.g., almost half of the atoms locate on the surfaces or at the interface in case of the top half of the octahedron particle with the size 1.6nm. The surface dipole and the interface dipole should be formed owing to the electron out of the surface to the vacuum and the local charge transfer from the gold particles to the TiO2 surface. These dipole effects might be effective and one of the reasons for the increase of the mean inner potential of gold particles.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 738: Symposium G – Spatially Resolved Characterization of Local Phenomena in Materials and Nanostructures , 2002 , G13.11
Copyright
Copyright © Materials Research Society 2003

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Haruta, M., Catal. Today 36, 153–166, (1997).Google Scholar
2. Smith, D. J., and McCartney, M. R., in Introduction to Electron Holography edited by Völkl, E., Allard, L. F. and Joy, D. C. (Kluwer Academic / Plenum Publishers, New York, 1999), pp. 87–124.Google Scholar
3. Spence, J. C. H., Acta Cryst. A49, 231–260, (1993).Google Scholar
4. Tsubota, S., Cunningham, D. A. H., Bando, Y., and Haruta, M., in Scientific Bases for Preparation of Heterogeneous Catalysts edited by Poncelet, G. et al. (Elsevier Science, New York, 1995), pp. 227–235.Google Scholar
5. Okumura, M., Tsubota, S., and Haruta, M., Proceedings of Nobel symposium 117 “The Physics and Chemistry of Clusters”, 307, (2001).Google Scholar
6. Buhl, R., Zeitschrift für Physik 155, 395–412, (1959).Google Scholar
7. Keller, M., Zeitschrift für Physik 164, 274–291, (1961).Google Scholar
8. Wang, Y. C., Chou, T. M., and Libera, M., presented at Microscopy Society of America meeting 1997, Cleveland, OH, 1997.Google Scholar
9. Gajdardziska-Jpsifovska, M. and Carim, A. H., in Introduction to Electron Holography edited by Völkl, E., Allard, L. F. and Joy, D. C. (Kluwer Academic / Plenum Publishers, New York, 1999), pp. 267–293.Google Scholar
10. Yada, K., J. Cryst. Soc. Japan 17 226–237 (1975).Google Scholar
11. Gajdardziska-Jpsifovska, M., McCartney, M. R., de Ruijter, W. J., Smith, D. J., Weiss, J. K., and Zuo, J. M., Ultramicroscopy 50 285–299 (1993).Google Scholar
12. Hirsch, P. B., Howie, A., Nicholson, R. B., Pashley, D. W., Whelan, M. J., in Electron Microscopy of Thin Crystals, (BUTTERWORTH, London, 1965), pp. 496.Google Scholar
13. Radi, G., Acta Cryst. A26, 41–56, (1970).Google Scholar