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Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P288
Growth and Oxidation of Pd/ZnO(001) nanoparticles
Nikolai Kasper 1 , Andreas Stierle 1 , Alexander Reicho 1 , Philipp Nolte 1 ,
Mitsuhiro Saito 1 , Thomas Wagner 1 , Helmut Dosch 1
1 Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, D 70569 Stuttgart, Ger-
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Understanding and controlling chemical reactions involving nanoparticles are important
milestones for future nanotechnologies and for the enhanced performance of catalysts
used in many applications. One key phenomenon is the oxidation behavior of
metal nanoparticles under industrially and environmentally relevant conditions, which
needs to be understood on a microscopic level.
We report in this work the results of the in-situ synchrotron X-ray diffraction study
of the high-pressure and high-temperature oxidation of Pd nanoparticles supported
on ZnO(001) substrates. These particles grow as truncated triangular bi-pyramid,
restricted by (111), (100) and (110) type of free faces [1]. We have observed the reversible
changes of the morphology of the particle facets vs. oxygen pressure (pO2 <
10 −4 mbar), however neither ( √ 5 × √ 5)R27 ◦ nor ( √ 6 × √ 6) surface oxides have been
found, which form during the oxidation of Pd(100) and Pd(111) single crystalline surfaces,
respectively [2, 3].
The details of the bulk oxide formation have been obtained and compared with the
results for Pd(100) [4] and Pd(111) [5] single crystalline surfaces and for Pd nanopaticles
deposited on other types of substrates, such as α-Al2O3(001) and MgO(001) [6]. We
demostrate that bulk PdO grows in the case of ZnO(001) - supported Pd nanoparticles
at much lower pressures than for the other mentioned systems. We suggested that this
feature is related to the polar nature of ZnO(001) surface.
Financial support of this work is acknowledged from the European Union under contract
no. NMP3-CT-2003-505670 (NANO2).
[1] C.R. Henry, Surf.Sci.Rep. 31 (1998) 231; C.T. Cambell, Surf.Sci.Rep. 27 (1997) 1.
[2] M. Todorova et al., Surf. Sci. 541 (2003) 101.
[3] G. Zheng, E.I. Altman, Surf. Sci. 462 (2000) 151.
[4] A.Stierle et al., J. Chem. Phys. 122 (2005) 044706; E. Lundgren et al., Phys. Rev.
Lett. 92 (2004) 046101.
[5] G. Ketteler, et al., J. of Am. Chem. Soc. 127 (2005) 18269.
[6] N. Kasper et al., Surf. Sci., in print.