Photon Factory Activity Report 2004 #22 Part B (2005)
Surface and Interface

9A/2004G285

Controlled Surface Structure of Cu species by Modified TiO2 (110) Surface withChemisorbed Acetic acidWang-Jae CHUN1, 2, Yuichiro KOIKE1, Kaoru IJIMA3, Hidenori ASHIMA2, Keisuke FUJIKAWA1,Kiyotaka ASAKURA1 and Yasuhiro IWASAWA4
1Catalysis Research Center Hokkaido University, Sapporo 001-0021, Japan, 2JST-CREST, Japan,
3
Department of Electronic Engineering, Yamanashi University, Takeda, Kofu 400-8510, Yamanashi,Japan, 4Department of Chemistry, Graduate School of Chemistry, The University of Tokyo, Hongo,Tokyo 113-0033, Japan.
0.01 ML. Chen et al., also reported that Cu is easily
aggregated to Cu metal particles when it is deposited on
the clean TiO2 (110) surface by STM.[4]On the other hand, Cu deposited on the modified
surface showed different behavior. The oscillations
damped monotonically. Note that the oscillations at-1
around 30 nm were completely different from those ofCu on the clean surface. It indicates that the modified
surface by CH3COOH hindered deposited Cu atoms toform Cu clusters. Considering the fact that the metalatoms are preferably located at the virtual cation
position,[1] we are proposing a model structure where Cu
atom adsorbed at the atop site of a bridging oxygen atom
and it bound to the adsorbed CH3COO molecules locatedby the side of the Cu atom through Cu-O (carboxylgroup) bonds. Further analysis is in progress.
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Introduction
The control of metal-oxide interface structure isindispensable to develop a new catalyst because themetal-oxide interface structure governs to determine theactive site structure and chemical properties. Our group
have recently revealed that surface structures of metalspecies which are bound to the surface anions such as
bridging oxygen atoms of TiO2 (110) and are strongly
correlated with the interface anion structures. [1-2] These
results suggest that the modification of the surface anion
structure may control the structures of the surface metalspecies.
Onishi et al. reported that carboxylic acids such as
formic acid and acetic acid form ordered (2×1) overlayers
on TiO2 (110) at their saturation coverages.[3] We
presume that the well defined chemisorbed carboxylic
acids on TiO2 (110) can be used as an organic modifier tocontrol the structures of metal clusters. The present work
describes a novel method for the control of Cu species aon modified TiO2 (110) surface and its surface structures
determined by Polarization-dependent Total Reflection
Fluorescence XAFS (PTRF-XAFS) technique.

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Results and Discussion
Figure 1 shows the PTRF-XAFS oscillations of 0.01
ML Cu on the clean TiO2 (110) and the modified surface
with acetic acid. For the clean surface all spectra wereidentical and showed oscillations characteristic to 3
dimensional Cu particles. It indicates that 3-dimensional
Cu particles are formed on the clean TiO2 (110) even at

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Experimental
TiO2(110) crystals were cleaned by Ar ion sputtering atroom temperature, followed by annealing at 1000 K untila sharp (1 × 1) LEED pattern was obtained. The cleansurface was modified by adsorbing acetic acid withsaturation coverage at room temperature. 0.01 ML Cu wasloaded to the modified surface by vacuum evaporation ofCu wire. The Cu coverages were monitored by XPS.
PTRF-XAFS was carried out with an in-situ PTRF-XAFS-8
measurement chamber (a base pressure of ca. 8 x 10 Pa)
and a Canberra 19-element SSD in a fluorescence modeat BL9A. XAFS analysis was performed with REX 2000
and FEFF 8. 0.

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-0 .05E // [001]E / / [001]-0.10-0 .1034567 -1 8k / 10 nm

91034567 -1 8k / 10 nm

910References[1] K. Ijima et al., Chem. Phys. Lett. 384 (2004) 134.
Figure 1 Observed Cu K-edge PTRF-EXAFS oscillations of Cu
on the clean TiO2(110) surface (a) and on the modifiedTiO2(110) by acetic acid (b).
[2] Y. Tanizawa et al., J. Phys. Chem. B 107 (2003) 12917.
[3] H. Onishi et al., Chem. Phys. Lett. 226 (1994) 111.
[4] D.A. Chen et al., Surf. Sci. 450(2000)78.
*wchun@cat.hokudai.ac.jp

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