The Eighth International Workshop on Oxide Surfaces (IWOX VIII)

<strong>The</strong> <strong>Eighth</strong> <strong>International</strong> <strong>Workshop</strong>
on Oxide Surfaces
(IWOX VIII)
15 – 20 January 2012
Hotel Tuc Blanc
Baqueira Beret, Spain

<strong>The</strong> <strong>Eighth</strong> <strong>International</strong> <strong>Workshop</strong> on Oxide Surfaces
(IWOX VIII)
Organising Committee:
15 – 20 January 2012
Hotel Tuc Blanc
Baqueira Beret, Spain
Prof Nicholas Harrison (Chair) (STFC Daresbury Laboratory & Imperial College London)
Prof Geoff Thornton (University College London)
Prof Renald Schaub (University of St Andrews)
Prof Dario Stacchiola (Brookhaven National Laboratory)
Prof Francesc Illas (Universitat de Barcelona)
IWOX <strong>International</strong> Board Members
Prof Nicholas Harrison (Chair) (STFC Daresbury Lab & Imperial College London)
Prof Scott Chambers (Pacific Northwest National Laboratory)
Prof Ulrike Diebold (Technical University of Vienna)
Prof Jacek Goniakowski (Institut des Nanosciences NSP)
Prof Falko Netzer (Uni. Gratz)
Prof Hiroshi Onishi (Kobe University)
Michael Bowker (University of Cardiff)
IWOX VIII Sponsors
Science & Technology Facilities Council
Omicron Nano Technology GmbH
SPECS Surface Nano Analysis GmbH
Createc

Sunday 15 January
21:00 – 22:30 Evening Reception
Monday 16 January
Daily Schedule & Programme
08:00 – 09:00 Breakfast
07:00 – 09:00 Registration
09:15 – 09:30 Welcome and Opening Remarks
Oral Session 1 Surface Structure
Session Chair – N.Harrison
09:30 – 10:15 Invited Speaker, Ulrike Diebold - Surface Structure In2O3 surface
10:15 – 10:30 R. Martinez-Casado - Ab initio calculation of the MgO(100) interaction with
He and Ne: a HF+MP2 and HF+MP2(B3LYP) comparison.
10:30 – 10:45 M.Watkins - Structure of Silica Nanoparticles in Solution from large scale,
DFT based, Molecular Dynamics Simulations.
10:45 – 11:00 G. Teobaldi - Scanning Tunnelling Microscopy imaging of Rutile TiO2(011)-
2x1: a Density Functional Study
11:00 – 11:30 Coffee Break
Oral Session 2 Water at Surfaces
Session Chair - S.Chambers
11:30 – 12:15 Invited Speaker, Miquel Salmeron - Adsorption and reactions of Water on
Metals and Oxides
12:15 – 12:30 X.Gong - New Insights into Reconstruction of Rutile TiO2(011).
12:30 – 12:45 R.Lindsay - Impact of Ambient Oxygen on the Surface Structure of
Cr2O3(0001)
12:45 – 13:00 M.Patel - Nanostructured TiO2 for Photovoltaic Hydrogen Production
13:30 – 14:30 Lunch
Afternoon Discussions
Oral Session 3 Polar Interfaces
Session Chair – H.Onishi
17:00 – 17:40 Invited Speaker, Akira Ohtomo - Quantum Transport at Polar Oxide
Interfaces
17:40 – 18:20 Invited Speaker, S.Chambers - Unraveling the Mystery of Conductivity at
Polar/Nonpolar Perovskite Interfaces.
18:20 – 18:35 C.Noguera - Polarity at the Nanoscale
20:00 – 21:00 Dinner

Tuesday 17 January
08:00 – 09:00 Breakfast
Oral Session 4 Structure and Reactivity
Session Chair – H.Brune
09:00 – 09:45 Invited Speaker, Francesc Illas - Modeling and Understanding Structure and
Reactivity of Ceria well defined Surfaces and Nanoparticles.
09:45 – 10:00 J.Zhang - A DFT+U study of CO/NOx Adsorption and Reaction at Au6/CeO2
(110) catalyst.
10:00 – 10:15 P.Luches - Interaction between Ag Nanoparticles and CeO2(111) ultrathin
films.
10:15 – 10:30 H.Idriss - Interactions of Rh, Pd, and RhxPdy (x, y = 4 or 6) on perfect and
defective ceria surfaces: Experimental and Computational studies.
10:30 – 11:00 Coffee Break
Oral Session 5 Metal Clusters at Surfaces
Session Chair – F.Illas
11:00 – 11:45 Invited Speaker, Harald Brune - Effect of the TiO2 Reduction State on the
Catalytic CO Oxidation on Supported Pt7Clusters.
11:45 – 12:00 R.Lazzari - Disclosing Growth Kinetics of Metal Nanoparticles through
Plasmonic response: the case of Ag/�-Al2O3(0001).
12:00 – 12:15 X.Shao - Tuning the Shape of Gold Particles by doping the Oxide Support.
12:15 – 12:30 S.Surnev - Alumina Supported Array of Transition Metal Nanoparticles:
Size-dependent Oxidation Kinetics.
13:30 – 14:30 Lunch
Afternoon Discussions
17:00 – 18:30 Poster Session 1
P1. X.Carrier - Surface EXAFS Characterization of Mo(Ni) Model Catalysts
supported on Alumina Single Crystals.
P2. R.Lazzari - What differs in the Hydroxylation of Supported MgO Thin Film
and MgO Bulk Surface ? A Combined STM/XPS Answer
P3. Q.Cuan - <strong>The</strong> Interaction of Water with High-index Anatase TiO2(105)
Surface: A First Principles Study.
P4. A.Samaniego - Comparing Surface Oxides on AZ31 and AZ61 Magnesium
alloys after a short time of Heat Treatment at 200ºC.
P5. D.Gao - Pd on MgO (001) : Transient Mobility Mechanisms.
P6. R.Lindsay - Oxygen adatoms on TiO2(110): Signature in Photoelectron
Spectroscopy
P7. R.Cavallotti - Adhesion Forces at zinc/α-Al2O3(0001) Interface.
P8. J.I.Flege - Interfactant-Mediated Growth of Rare-Earth Oxides on Silicon
20:00 – 21:00 Dinner

Wednesday 18 January
08:00 – 09:00 Breakfast
Oral Session 6 Oxide Thin Films
Session Chair – M.Salmeron
09:00 – 09:45 Invited Speaker, Hajo Freund - Thin Oxide Films: <strong>The</strong> Expected and the
Unexpected.
09:45 – 10:00 J.Goniakowski - Shape and Structure of Supported MgO(100) Nano-Islands:
Role of the Adhesion at the Metal/Oxide Interface.
10:00 – 10:15 H.Kulenbeck - V/Ti and Mo/Ti mixed Oxide Layers on TiO2(110).
10:15 – 10:30 D.Grinter - Carboxylate Interactions with Model Titania Surfaces
10:30 – 11:00 Coffee Break
Oral Session 7 Catalysis and Rational Design
Session Chair – G.Thornton
11:00 – 11:45 Invited speaker, Gianfranco Pacchioni - <strong>The</strong>ory of Oxides Doping. Towards
a Rational Design of New Catalytic Materials.
11:45 – 12:00 J.Jupille - Active Oxygen Species in CO Oxidation on Au/TiO2(110)
evidenced during in situ Photoemission Analysis.
12:15 – 12:30 U.Martinez - Structure and Reactivity of Steps on Rutile TiO2(110)
12:30 – 12:45 L.Mino - Surface Properties and Reactivity of TiO2 Nanocrystals: a
Combined Experimental and ab initio study.
13:30 – 14:30 Lunch
Afternoon Discussions
19:30 – 23:30 Conference Dinner

Thursday 19 January
08:00 – 09:00 Breakfast
Oral Session 8 Photocatalysis
Session Chair – Z.Dohnalek
09:00 – 09:45 Invited speaker, Hiroshi Onishi - Toward Surface Science of Metal Oxide
Photocatalysts.
09:45 – 10:00 C.Wöll - Photocatalysis on Oxides: Case Studies on Rutile and Anatase TiO2
Single Crystals Surfaces.
10:00 – 10:15 M.Chiesa - Local Environment of Ti 3+ Ions in Reduced TiO2 Through Spin
Density Studies.
10:15 – 10:30 Y.Wang - Photoactivity of TiO2 Rutile and Anatase Surfaces.
10:30 – 11:00 Coffee Break
Oral Session 9 Catalysis
Session Chair – G.Pacchioni
11:00 – 11:45 Invited speaker, Zdenek Dohnalek - Preparation, Characterization, and
Catalytic Activity of Model WO3 and MoO3 Catalysts.
11:45 – 12:00 E.Ahmad - <strong>The</strong> Phase Stability of LaMnO3 and its Surfaces: A Hybrid
Density Functional Study of an Alkaline Fuel Cell Catalyst.
12:00 – 12:15 C.Yim - <strong>The</strong> Growth of Pd Islands on Rutile TiO2(110)-(1×1)
12:15 – 12:30 S.Tosoni - DFT Study of the Electronic Structure of F-doped Titania
13:30 - 14:30 Lunch
17:00 – 18:30 Poster Session 2
P9. C.O’Brien - Hydrogenation of Unsaturated Hydrocarbons over Fe3O4
Supported Pd Nanoparticles: Activation and Reactivity of the pro-chiral
Molecule Isophorone.
P10. H.Noei - Probing the Mechanism of Low Temperature CO Oxidation on
Au/ZnO Catalysts by Vibrational Spectroscopy.
P11. S.Altieri - Temperature and Field Dependent Soft x-ray Absorption (XAS)
and Magnetic Circular Dichroism (MCD) study of self-doped 3d Oxide
Nanostripes.
P12. M.Wolf - Self-Trapping of Holes at the Surface of Monoclinic Zirconium
Dioxide.
P13. S.Adamovsky - Heats of Adsorption and Surface Reaction for Carbon
Monoxide and Oxygen on Pd Nanoparticles as determined by UHV Single
Crystal Adsorption Microcalorimetry.
P14. D.Stacchiola - Controlling the Structure of CeO2 Nanoparticles grown on
Cu2O Thin Films.
P15. A.Meyer - Oxidation and Reduction of Ultrathin Silver Films on Ni(111).
P16. C.Gionco – Structural Properties and Photoactivity of Mixed Oxides ZrO2-
TiO2.
P17 I.Hicham - <strong>The</strong> Interaction of Biomolecules with Model Surfaces: Cystiene
and RGD on TiO2 (110).
20:00 – 21:00 Dinner

Friday 20 January
08:00 – 09:00 Breakfast
Oral Session 10 Surface Reactivity
Session Chair – D.Stacchiola
09:00 – 09:45 R.Bechstein - Reactivity vs. Morphology – Steps on TiO2(110)
10:00 – 10:15 T.Y.Chang - Direct Imaging of Pt Atoms on TiO2 (110) Surface by Aberration
Corrected Scanning Transmission Electron Microscopy.
10:15 – 10:30 F.Sanches - Ab initio Study of Anatase TiO2 Surfaces for Nanoparticle
Modelling in Solar Hydrogen Production.
10:30 – 10:45 S.Wendt - Direct Evidence of Ethanol Dissociation on Rutile TiO2(110)
10:45 – 11:00 Coffee Break
11:00 – 11:30 Closing remarks, end of conference.

Abstracts for Orals
STM investigations of pure and Sn-doped In2O3 surfaces
Ulrike Diebold*
Inst. of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, A-1040
Vienna, Austria
Tin-doped Indium Oxide (ITO) is a transparent conducting oxide that finds wide use in a variety of
industrial applications such as gas sensing, solar cells, and organic light-emitting diodes. While
the surface properties of this material play a key role in these and many other applications,
surprisingly little information exists about its fundamental surface characteristics.
We will present LEED, XPS, UPS, RHEED, LEED, and STM results of epitaxial ITO films, grown
on Yttria-stabilized Zirconia, and discuss geometric models that are derived from atomicallyresolved
STM images and DFT calculations [1, 2]. Surface polarity seems to play a major role in
the stability and surface structure of ITO films. <strong>The</strong> (111) surface of the bixbyite structure is nonpolar
and ITO(111) surfaces are essentially bulk-terminated with a 1x1 periodicity. <strong>The</strong> apparent
topology in STM images is dominated by the physical corrugation.
<strong>The</strong> (100) surface is polar and consequently much more complex. Atomically-resolved STM
images of Sn-doped films show a rich structure that can be reconciled with a dimerization of
surface O atoms that is predicted by theoretical calculations, as well as adsorbates at specific
lattice sites. We will also present results on (undoped) In2O3 single crystals. <strong>The</strong>se are pale yellow
at room temperature and show a reversible darkening upon heating in UHV. <strong>The</strong> as-grown
samples have the form of small cubes with (100)-oriented facets. While the LEED pattern is sharp
and compatible with the one from epitaxial thin films, STM shows a significant disorder in the
atomic-scale structure. <strong>The</strong> observed preference for double-height steps suggests that one type of
termination is preferred.
[1] E. Morales, Y. He, B. Delley, and U. Diebold, New Journal of Physics, 10 (2008) 125030;
[2] E. Morales and U. Diebold, Applied Physics Letters, 95 (2009) 253105
[3] D. Hagleitner et al., submitted
______________
*diebold@iap.tuwien.ac.at

Ab initio calculation of the MgO(100) interaction with He and Ne:
a HF+MP2 and HF+MP2(B3LYP) comparison.
R. Martinez-Casado1 G. Mallia1 and N. M. Harrison1,2
1 Department of Chemistry, Thomas Young Centre, Imperial College, London SW7 2AZ, UK
2 STFC, Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK
He-atom scattering from surfaces is a well established and valuable tool for characterizing the
structure of periodic surfaces, determining gas-surface interaction potentials, and investigating the
presence of defects and adsorbates. Unlike other techniques (e.g., LEED, STM or FIM), He-atom
scattering causes no damage to the surface, is very surface sensitive, as it probes only the
outermost layer, and does not suffer from the surface charging effects, which plague, for instance,
photoelectron spectroscopy and electron diffraction. <strong>The</strong> correct interpretation of the experimental
data requires an accurate description of the He-surface interaction potential. Empirical models of
the surface atom potential, which introduce an uncontrolled approximation to the interpretation of
the data, have been used but are limited to few systems, where interactions are reasonably well
understood. A quantum-mechanical description of the interactions has not previously been
possible, because the dominant methodologies for dealing with extended systems are based on
Hartree-Fock (HF), density functional theory (DFT) and/or hybrid exchange DFT approaches,
which do not describe correctly London dispersion forces, vital for the scattering process. In our
most recent works [1,2], we show that a qualitatively correct description of the (He,Ne)-MgO
interaction potential can be obtained by applying second order Rayleigh Schroedinger perturbation
theory to calculate the correlation energy contribution to the London dispersion interaction based
on,-single particle orbitals from either Hartree-Fock theory or hybrid-exchange density functional
theory as the reference state.
[1] R. Martínez-Casado, G. Mallia and N.M. Harrison, CHEMICAL COMMUNICATIONS
47, 4385 (2011)
[2] R. Martínez-Casado, G. Mallia and N.M. Harrison, CHEMICAL COMMUNICATIONS
(accepted, 2011) DOI: 10.1039/c1cc14623h

Structure of silica nanoparticles in solution from large scale, DFT based, molecular
dynamics simulations
M. Watkins and A. L. Shluger
Silica finds many applications due to its optical properties, biocompatibility and ease of surface
modification, e.g. high-frequency devices, substrates for silicon in microelectronics, for adhesion of
polymers, drug delivery vehicles. Characterisation of the surface of silica is complicated due to the
amorphous nature of the material and a consequent lack of probes that can reveal surface
structure in atomistic detail. A further complication is the ready hydroxylation of the material under
many environmental conditions. Surface hydroxylation is extremely important, providing the
anchoring points for further functionalization and determining the interaction of the material with
water – bare siloxane groups (O-Si-O) are strongly hydrophobic, forming almost no hydrogen
bonds with adsorbed water, whilst silanol groups (Si-OH) lead to strong hydrophilic interactions.
<strong>The</strong>re have been extensive efforts in recent times to build model surfaces using a variety of
simulation approaches [1-4], mainly focusing on flat surfaces with various degrees of idealisation –
from crystalline α-quartz surfaces to amorphous materials produced by various protocols. We take
a different approach and consider the properties of silica nanoparticles – these offer several
chemically distinct sites, such as under-coordinated surface species, and we can tune their
properties by starting from silica particles of different stability.
Three model silica nanoparticles with diameter of ~1 nm were generated by simulated annealing of
an initial structure developed by Ya and Foster[5], representing clusters of increasing stability in
vacuum. In addition a smaller cluster, believed to be the global minima in vacuum[6], was
considered. <strong>The</strong>se four models were fully solvated by hundreds of water molecules and, using a
highly efficient implementation of DFT based molecular dynamics[7], their change in structure with
time during exposure to water was studied. We identify a variety of surface reactions, similar to
those observed by Garofolini and other studies[3], but also note that through the motion of
generated hydronium ions, correlated reactions occur at surface sites with large separations.
Metastable particles are found after only ca. 5 ps of simulation and we have examined the
functional groups present at their surface.
<strong>The</strong>se silica systems can find direct use as models of scanning probe microscope tips in solution.
We will show results demonstrating how the tip and surface structure, and their interaction with
aqueous solution, can be probed using the atomic force microscope.[8]
1. Zhang, H., et al., <strong>The</strong> water-amorphous silica interface: analysis of the Stern layer and surface conduction. J Chem
Phys, 2011. 134(2): p. 024705.
2. Pedone, A., et al., FFSiOH: a New Force Field for Silica Polymorphs and <strong>The</strong>ir Hydroxylated Surfaces Based on
Periodic B3LYP Calculations. Chemistry of Materials, 2008. 20(7): p. 2522-2531.
3. Mahadevan, T.S. and S.H. Garofalini, Dissociative Chemisorption of Water onto Silica Surfaces and Formation of
Hydronium Ions. Journal of Physical Chemistry C, 2008. 112(5): p. 1507-1515.
4. Yang, J. and E. Wang, Water adsorption on hydroxylated -quartz (0001) surfaces: From monomer to flat bilayer.
Physical Review B, 2006. 73(3): p. 035406.
5. Ma, Y., A.S. Foster, and R.M. Nieminen, Reactions and clustering of water with silica surface. J Chem Phys, 2005.
122(14): p. 144709.
6. Flikkema, E. and S.T. Bromley, Dedicated Global Optimization Search for Ground State Silica Nanoclusters:
(SiO2)N(N= 6−12). <strong>The</strong> Journal of Physical Chemistry B, 2004. 108(28): p. 9638-9645.
7. Vandevondele, J., et al., : Fast and accurate density functional calculations using a mixed Gaussian and plane waves
approach. Computer Physics Communications, 2005. 167(2): p. 103-128.
8. Watkins, M. and A.L. Shluger, Mechanism of Contrast Formation in Atomic Force Microscopy in Water. Physical Review Letters,
2010. 105(19): p. 196101.

Scanning Tunnelling Microscopy imaging of Rutile TiO2(011)-2x1: a Density
Functional Study
G. Teobaldi
Stephenson Institute for Renewable Energy and Surface Science Research Centre
Department of Chemistry, University of Liverpool, L69 3BX Liverpool, UK
e-mail: g.teobaldi@liv.ac.uk
We report a Density Functional <strong>The</strong>ory (DFT) study of the simulated Scanning Tunnelling
Microscope (STM) appearance of the 2x1 reconstruction of the Rutile TiO2(011) surface.
By combining standard DFT (PBE-GGA [1]), hybrid DFT (HSE06 [2]) and on-site corrected local
spin density approximation (LSDA+U [3]), we show the recently amended structure of TiO2(011)-
2x1 [4,5] to be consistent with available experimental data in terms of zig-zag bright patterns as
imaged by STM for positives biases [5-8]. <strong>The</strong> reported change in STM contrast for different
tunnelling conditions [5] is elucidated in terms of the subtle balance between surface geometry and
different vacuum decay lengths of the topmost Ti(3d) and O(2p) states. In line with previous results
[5], for close tip-surface distances we model the staggered bean-like bright features [5] to be
pinned at the topmost two-fold coordinated O atoms. Conversely, the STM contrast farther from the
surface is found to be governed by the longer decay length of the topmost Ti(3d) states with
respect to the O(2p) states. Thus, we model the rounded features of the zig-zag pattern [5-8] to be
pinned in proximity of the topmost five-fold coordinated Ti atoms.
Bardeen STM simulations with explicit inclusion of the (W) tip electronic structure confirm these
conclusions. Notably, depending on the tip sub-apex structure the two STM contrasts may or may
not be resolved for the same applied bias.
<strong>The</strong>se findings are finally discussed with respect to the limitations of the (PBE-)GGA description of
Ti(3d) states and the ensuing complications for the simulated STM-imaging of O-terminated titania
structures at relative large tip-surface distances.
[1] Phys. Rev. Lett. 77, 3865 (1996); [2] J. Chem. Phys. 118, 8207 (2003); J. Chem. Phys. 124, 219906
(2006); [3] Phys. Rev. B 77, 045118 (2008); [4] Phys. Rev. Lett. 101, 185501 (2008); [5] Surf. Sci. 603, 138
(2009); [6] Phys. Rev. Lett. 93, 036104 (2004); [7] Surf. Sci. 600, 4407 (2006); [8] Science 317, 1052 (2007);
[9] Nanotechnology 19, 495304 (2008).

Adsorption and reactions of water on metals and oxides
Miquel Salmeron. Materials Science Divison, Lawrence Berkeley National Laboratory and
Materials Science and Engineering Department, University of California at Berkeley
<strong>The</strong> solid-water interface is one of the most important systems, and has been studied over many
decades with surface science tools. Questions that still need to be answered for a fundamental
understanding of wetting and reactivity include the nature of the water-surface chemical bond and
the H-bonding structure of the surface layers, first in contact with the substrate and then as
multilayers. Chemical reactions involve H-O bond rupture and formation of surface hydroxyl
species. Using a combination of microscopy (STM) and spectroscopy tools (XPS and XAS), we
have investigated water adsorption and reactions on a series of oxide surfaces (TiO2, Fe2O3,
SiO2, Al2O3 and MgO) as well on metals (Ru, Pd) and oxygen covered metals surfaces. <strong>The</strong>se
studies indicate that on oxide surfaces partial water dissociation is a common phenomenon
occurring on the first layer. Restructuring of the surface oxide also is observed as water competes
with O for metal bonds. Finally the reactions of water with graphene layers on metals will be
discussed

New insights into reconstruction of rutile TiO2(011)
Qian Cuan a , Junguang Tao b , Xue-Qing Gong a , and Matthias Batzill b
a State Key Lab of Chemical Engineering, Centre for Computational Chemistry and Research
Institute of Industrial Catalysis, East China University of Science and Technology, 130 Meilong
Road, Shanghai 200237, P.R. China
b Department of Physics, University of South Florida, Tampa, Florida 33620, United States
<strong>The</strong> surface structure determined by vacuum surface science studies is often taken as the relevant
surface structure for explaining chemical functionalities of materials. This implies a picture of a rigid
surface, with only small relaxations if molecules adsorb on it. Through a combination of scanning
tunnelling microscopy (STM) and first-principles density functional theory (DFT) calculations, we
determined that the (011) surface of rutile titanium dioxide (TiO2), with a native 2×1 reconstruction,
is capable of restructuring, which enables the surface to exhibit high chemical activity toward
specific adsorbates.
Figure 1. Calculated structures (top row:
side view, bottom row: top view against [001]
direction) of a) bulk-truncated 1×1, b) most
stable vacuum 2×1 and c) restructured 2×1
rutile TiO2(011) surfaces. <strong>The</strong> bulk Ti atoms
are in grey and O in red. <strong>The</strong> O in green and
Ti in yellow form the sandwich-like Ti2O4 unit
(square in black dotted line) and the O in
blue and Ti in purple build the trough of the
2×1 surfaces. <strong>The</strong> arrows in a) indicate the
movement of surface atoms to form the 2×1
surface reconstruction shown in b).
Figure 2. STM of acetic acid
adsorption on TiO2(011) surface. a)
For small acetic acid exposures
adsorption only occurs at surface
defect sites. b) With increasing acetic
acid exposure quasi-1D acetate
clusters are formed that eventually
cover most of the surface c). A
detailed structure of the acetate
clusters are shown in d). e) Quasi-3D
view of an acetate cluster, highlighting
the increased height of the center row
protrusion.
Our calculations showed that the bulk-truncated rutile TiO2(011) (Fig.1a) would undergo a 2×1
reconstruction and end up with a very stable structure (Fig.1b). However, through further
restructuring, such vacuum structure could turn to be quite active (Fig.1c), which can explain the
rather high activity of TiO2(011) during interaction with acetic acid molecules (Fig. 2). In particular,
the formation of rows of adsorbates is in line with the calculation results that the restructuring
occurs via the translation of a whole row of surface structural units. <strong>The</strong>se results show that some
metal oxides surfaces can change their structural confirmation to enable adsorption and thus
promote reactions that are not possible on the vacuum terminated surface.

Impact of ambient oxygen on the surface structure of Cr2O3(0001)
Rob Lindsay 1 , Oier Bikondoa 2,3 , Wolfgang Moritz 4 , Xavier Torrelles 5 , Hyojung Kim 6,7 , Geoff
Thornton 8
1. Corrosion and Protection Centre, School of Materials, <strong>The</strong> University of Manchester,
Sackville Street, Manchester, M13 9PL, UK
2. XMaS, UK-CRG , ESRF, 6 rue Jules Horowitz, F-38043 Grenoble cedex, France
3. Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
4. Department of Earth and Environmental Sciences, University of Munich, <strong>The</strong>resienstrasse
41, 80333 Munich, Germany
5. Institut de Ciència de Materials de Barcelona (CSIC), Campus UAB, 08193 Bellaterra, Spain
6. ESRF, 6 rue Jules Horowitz, F-38043 Grenoble cedex, France
7. Department of Materials Science and Engineering and the Centre for OLED, Seoul National
University, Seoul 151-744, Korea
8. London Centre for Nanotechnology and Department of Chemistry, University College
London, 20 Gordon Street, London WC1H OAJ, UK
Fundamental experimental studies of Cr2O3(0001) are motivated both by a desire to understand
the stabilization of polar oxide surfaces, and the importance of chromia in various applications, e.g.
corrosion control and heterogeneous catalysis. Significant nanoscale insight has already been
gained from such measurements, although they have largely been restricted to ultra high vacuum
(UHV). This limits their utility for mechanistic interpretation of technological performance. We
address this issue here, employing surface X-ray diffraction (SXRD) to elucidate the geometric
structure of Cr2O3(0001) as a function of a key environmental parameter, namely the oxygen partial
pressure.
In UHV the surface is found to exhibit a partially occupied double layer of chromium atoms. At an
oxygen partial pressure of 1x10 -2 mbar, the surface is determined to be terminated by chromyl
species (Cr=O), clearly demonstrating that the presence of oxygen can significantly influence the
structure of Cr2O3(0001). <strong>The</strong> UHV surface geometry is largely consistent with that derived from
previous quantitative low energy electron diffraction (LEED) measurements, although there are
some small differences in atomic coordinates and fractional layer occupancies. Ab initio
calculations performed to date, including two examining surface structure as a function of oxygen
partial pressure, fail to predict either of the two experimentally determined structures. This
outcome is largely a result of the theoretical work being performed on periodic slabs with small unit
cells, precluding mimicry of fractionally occupied surface atomic layers.

Abstract
Nanostructured TiO2 for Photovoltaic
Hydrogen Production
Monica Patel, Giuseppe Mallia, Leandro Liborio,
Nicholas Harrison and James Durrant
Department of Chemistry, Imperial College London, London, SW7 2AZ
Tel: +44 (0) 207 594 8160; Fax: +44 (0) 207 594 6757; Email:
monica.patel10@imperial.ac.uk
In order to improve the solar-to-fuel efficiencies in water splitting for hydrogen production,
enhancement of the fundamental understanding of the photocatalysis is required. <strong>The</strong> surface
chemistry of rutile TiO2 has been studied using the (110) surface as a model system. <strong>The</strong>
adsorption of water on the rutile TiO2(110) surface has been investigated using hybrid-exchange
density functional calculations. <strong>The</strong> slab approach is used to simulate the (110) surface, and
different adsorption modes have been studied; the effect of water coverage on the binding energy
and electronic structure is uncovered. Alongside this, the interactions between adsorbates on the
surface are considered. <strong>The</strong> results show that to consider intermolecular interactions is vital for
understanding how the first layer of water adsorbs, and that water coverage has a critical influence
on the nature of these interactions.

Quantum Transport at Polar Oxide Interfaces
Speaker: Akira Ohtomo
Affiliation: Department of Applied Chemistry, Tokyo Institute of Technology, Tokyo 152-
8552, Japan
Atomic-scale control of oxide heteroepitaxy is of growing importance from the viewpoints of
fundamental physics and device applications. Many of intriguing physical phenomena occur in
naturally layered structures of transition-metal oxides, leading to recent focuses on "epitaxial"
design of new compounds upon the layer-by-layer growth of artificial superstructures. We have
been studying magnetotransport properties of high-mobility electrons at polar oxide
heterointerfaces. In the first case, we have created a metallic state in atomically abrupt
heterointerface between two band insulators, SrTiO3 and LaAlO3 [1], in which naturally arising
polarity discontinuity introduces high-mobility electrons in SrTiO3. Dramatic magnetoresistance
oscillations appeared at low temperatures. Moreover, electric-field induced metal-insulator and
superconductor-insulator transitions have been demonstrated. <strong>The</strong> second example is
ZnO/MgZnO heterostructures, in which we have recently succeeded in observing fractional
quantum Hall effect [2]. <strong>The</strong>se results have implications for all oxide heteroepitaxial devices. In
particular, the high mobilities achieved present the possibility to combine the world of oxides
(superconductors, multiferroics, colossal magnetoresistance) with the world of semiconductor
heterostructures.
[1] A. Ohtomo and H. Y. Hwang, Nature 427, 423-426 (2004).
[2] A. Tsukazaki, A. Ohtomo, M. Kawasaki, et al. Nat. Mater. 9, 889-893 (2010)

Unraveling the mystery of conductivity at polar/nonpolar perovskite interfaces
Scott A. Chambers
Fundamental and Computational Sciences Directorate
Pacific Northwest National Laboratory
Richland, WA 99352 USA
Complex oxides exhibit a rich array of properties as a result of the degrees of freedom that can be
achieved by the choice of metal cations. This richness has been built upon by preparing interfaces
of dissimilar perovskites. One of the most interesting and widely investigated systems of this kind is
the LaAlO3/SrTiO3(001) (LAO/STO) heterojunction [1-3]. Despite the fact that both materials are
band insulators, their interface can exhibit electronic conductivity, at least when prepared under
certain conditions. <strong>The</strong>se results have been widely interpreted as being due to an electronic
reconstruction (or charge transfer) resulting from the polarity mismatch between LAO and STO,
giving rise to a two-dimensional electron gas on the STO side of the interface. This charge transfer
is thought to eliminate the interface dipole, which if not removed by some means, would cause the
electrostatic potential within the LAO to diverge. However, it is also known that this interface
exhibits significant cation mixing, and certain intermixed configurations have been shown
theoretically to eliminate the interface dipole, in addition to inducing conductivity by unintentional
La doping of the underlying STO [4-7].
Inasmuch as the LAO/STO interface has been very heavily studied, it is of interest to explore other
related materials systems. To this end, we have investigated the LaCrO3/SrTiO3(001) (LCO/STO)
heterojunction, as prepared by MBE [8]. Like LAO/STO, LCO/STO is a III-III/II-IV perovskite
interface and should exhibit interface conductivity for the same reasons that LAO/STO should be
conductive. Indeed, core-level and valence-band x-ray photoemission spectra yield band offsets
and potential gradients within the LaCrO3 sufficient to trigger an electronic reconstruction to
alleviate the polarity mismatch [9]. Yet, the interface is insulating. Based on first principles
calculations, we attribute this unexpected result to interfacial cation mixing combined with charge
redistribution within CrO2 layers, enabled by low-lying d states within LaCrO3, which suppresses an
electronic reconstruction.
[1] M. Huijben, A. Brinkman, G. Koster, Rijnders, H. Hilgenkamp, D. H. A. Blank, Adv. Mater. 21, 1665
(2009).
[2] J. Mannhart, D. G. Schlom, Science 327, 1607 (2010).
[3] R. Pentcheva, W. E. Pickett, J. Phys: Cond. Mat. 22, 043001 (2010).
[4] S. A. Chambers, M. H. Engelhard, V. Shutthanandan, Z. Zhu, T. C. Droubay, L. Qiao, P. V. Sushko, T.
Feng, H. D. Lee, T. Gustafsson, E. Garfunkel, A. B. Shah, J.-M. Zuo, Q. M. Ramasse, Surf. Sci. Rep. 65,
317 (2010).
[5] L. Qiao, T. C. Droubay, V. Shutthanandan, Z. Zhu, P. V. Sushko, S. A. Chambers, J. Phys.: Condens.
Matter 22, 312201 (2010).
[6] L. Qiao, T. C. Droubay, T. C. Kaspar, P. V. Sushko, S. A. Chambers, Surf. Sci. 605, 1381 (2011).
[7] L. Qiao, T. C. Droubay, T. Varga, M. E. Bowden, V. Shutthanandan, Z. Zhu, T. C. Kaspar, S. A.
Chambers, Phys. Rev. B 83, 085408 (2011).
[8] L. Qiao, T. C. Droubay, M. E. Bowden, V. Shutthanandan, T. C. Kaspar, S. A. Chambers, Appl. Phys.
Lett. 99, 061904 (2011).
[9] S. A. Chambers, L. Qiao, T. C. Droubay, T. C. Kaspar, B. Arey, P. V. Sushko, Phys. Rev. Lett., in press
(2011).

Polarity at the nanoscale
Claudine Noguera and Jacek Goniakowski
Institut des Nanosciences de Paris, UMR 7588, CNRS & Université Paris 06,
4 place Jussieu, 75252 Paris cedex 05, France
Extended polar objects present an electrostatic instability which requires substantial modifications
of the surface charge density in order to become stable. Microscopic surface processes related to
polarity compensation have been extensively studied in the last decades, also as a potential tool
for tuning surface electronic and structural properties [1].
More recently it has become clear that polarity does also concern nano-objects, but that the
relevant electrostatic forces and the response they induce differ from the known ones [2]. Indeed,
below a critical size nano-objects may sustain finite dipole moments which drive strongly size- and
dimensionality- dependent properties. Moreover, at small sizes, polarity effects may extend beyond
the surface region and drive structural transformations of the entire object, resulting in novel
structures, with no bulk counterparts.
Since oxide nano-objects, such as ultra-thin films, are often synthesized on metal substrates, their
polarity characteristics are additionally modified by the electrostatic coupling between their
structure and the interface charge transfer [3].
In this presentation, we will analyse polarity effects in nano-objects of various dimensionality: ultrathin
films grown along polar directions, nano-islands with polar edges, three-dimensional clusters
with polar facets. We will highlight the manifestations of electrostatic forces as a function of
dimensionality, size and shape of the objects. This will reveal new phenomena, such as the
existence of uncompensated polarity or of electric gradients on polar facets/edges. <strong>The</strong> concepts
will be exemplified on MgO nano-objects of various dimensionality and shape, unsupported or
supported on metal substrates.
[1] J. Goniakowski, F. Finocchi, C. Noguera, L. Giordano, Rep. Prog. Phys. 2008 71, 016501
[2] J. Goniakowski, C. Noguera, L. Giordano, Phys. Rev. Lett 2004 93, 215702; 2007 98 205701; J.
Goniakowski, J. Noguera, Phys. Rev. B 2011 83, 115413
[3] J. Goniakowski, C. Noguera, Phys. Rev. B 2009 79, 155433; J. Goniakowski, L. Giordano, J. Noguera,
Phys. Rev. B 2010 81, 205404

Modeling and understanding structure and reactivity of ceria well defined
surfaces and nanoparticles
Francesc Illas
Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB),
Universitat de Barcelona, C/ Martí i Franquès 1, 08028 Barcelona, Spain
Ceria (CeO2) is an interesting material of paramount importance is various technologies and,
in particular, in catalysis. One of the key properties responsible for the special function of
ceria-based heterogeneous catalysts is the facile reducibility of CeO2, which involves the
Ce 4+ ↔ Ce 3+ process. This redox process can be triggered either by direct electron transfer
from metals adsorbed over a ceria surface or by oxygen release. Both processes result in
the appearance of Ce 3+ cations with highly localized Ce (4f 1 ) electrons. This is precisely the
main reason for the difficulties encountered when attempting to describe the electronic
structure of ceria based materials using standard computational methods derived from
Density Functional <strong>The</strong>ory. In fact, the usual Local Density Approach (LDA) and the
Generalized Gradient Approach (GGA) forms of the universal exchange-correlation potential
are unable to properly describe the localized character of the Ce 4f 1 electrons in Ce 3+ cations
[1]. Other approaches such as the so-called LDA+U (or GGA+U) or hybrid functional which
contain a fraction of non-local Fock exchange provide a more physically sound description of
partly reduced ceria (CeO2-x) bulk and surface [1] although this is not free of problems. This
is illustrated taking the oxidation state of Au on CeO2(111) as a case study [2,3]. <strong>The</strong> study
of ceria nanoparticles introduces yet several additional complications due to the difficulty to
predict the most stable structure of a given particle and, for non-stoichiometric samples, of
handling the electronic isomers differing in the position of the Ce 3+ cations. <strong>The</strong> combined
use of global optimization procedures using interatomic potentials and of DFT calculations
offers a physically sound description and permits one to make important predictions about
the properties of these interesting systems [4-6]. Finally, we will discuss relevant results for
the technologically important Pt/ceria catalysts: (i) electron transfer from the Pt nanoparticle
to the support, and (ii) oxygen transfer from ceria to Pt and show that the latter requires the
presence of nanostructured ceria in close contact with Pt and, thus, is inherently a nanoscale
effect [7].
References
[1] C. Loschen, J. Carrasco, K. M. Neyman and F. Illas, Phys. Rev. B, 75 (2007) 035115
[2] N. J. Castellani, M. M. Branda, K. M. Neyman and F. Illas, J. Phys. Chem. C, 113 (2009) 4948
[3] M. M. Branda, N. J. Castellani, R. Grau-Crespo, N. H. de Leeuw, N. C. Hernandez, J. F. Sanz, K.
M. Neyman F. Illas, J. Chem. Phys., 131 (2009) 094702
[4] A. Migani, K M. Neyman, F. Illas and Stefan T. Bromley, J. Chem. Phys., 131, (2009) 064701
[5] A. Migani, G. N. Vayssilov, S. T. Bromley, F. Illas and K. M. Neyman, Chem. Commun., (2010)
5936-5938
[6] A. Migani, G. N. Vayssilov, S. T. Bromley, F. Illas and K. M. Neyman, J. Mater. Chem., 20 (2010)
10535
[7] G. N. Vayssilov, Y. Lykhach, A. Migani, T. Staudt, G. P. Petrova, N. Tsud, T. Skála, A. Bruix, F.
Illas, K. C. Prince, V. Matolín, K. M. Neyman, J. Libuda, Nature Materials, 10 (2011) 310

A DFT+U study of CO/NOx adsorption and reaction at Au6/CeO2 (110) catalyst
Jie Zhang, Xue-Qing Gong, and Guan-Zhong Lu
State Key Lab of Chemical Engineering, Centre for Computational Chemistry and Research
Institute of Industrial Catalysis, East China University of Science and Technology, 130
Meilong Road, Shanghai 200237, P.R. China
<strong>The</strong> adsorption of CO and NOx at supported Au6/CeO2(110) catalyst and their redox reaction
were studied by density-functional theory (DFT) within generalized gradient approximation
method corrected by on-site Coulomb interaction (GGA+U). It was found that CO strongly
adsorbed on the top site of Au cluster while the interaction between NO and surface was
relatively weaker. By contrast, N2O2 dimer species was found to have strong adsorption
energy at the interface between CeO2 support and gold metal. From calculated energetics of
the whole reaction process, we can conclude that reaction between CO and N2O2 can occur
rather easily with activation energy of ~0.4 eV. However, the second step to eliminate N2O
through unimolecule collision needs higher temperature.
Fig1. a
Fig1. b
Fig1. c
Fig1. (a) represents the spin charge density distribution of Au6/CeO2; (b) represents the spin charge
density distribution after adsorption of CO at Au6/CeO2 (CO adsorbs on top site of Au6); (c) represents
the spin charge density distribution after adsorption of CO+N2O2 at Au6/CeO2 (CO adsorbs on top site of
Au6, N2O2 adsorbs at the interface of CeO2 and Au6 cluster).
By calculating the electronic structures, we also found that CeO2 plays a role of storing
electrons in Au6/CeO2 (110) catalyst (Fig1. a). Two spin-polarized electrons are localized into
Ce 4f empty orbital after Au6 cluster adsorbs at CeO2 (110), and it is not affected by CO
adsorption at Au (Fig1. b). However, when a N2O2 dimer species forms at the Ce reduced by
Au, it can be negatively charged so that the occurrence of spin electrons at these two Ce is
suppressed. Interestingly, we also found that the adsorbed N2O2 may take different
configurations and the one at the Au6/CeO2 (110) interface (Fig1. c) is relatively far away
from the CeO2 support. In this case, the charge transfer from Au to the surface Ce occurs
again, and the N2O2 turns to be reactive for CO oxidation.

Interaction between Ag nanoparticles and CeO2(111) ultrathin films
P. Luches 1 , F. Pagliuca 1,2 , S. Valeri 1,2 , G. Preda 3 , G. Pacchioni 3
1 S 3 , Istituto Nanoscienze, CNR, Modena, Italy
2 Dipartimento di Fisica, Università di Modena e Reggio Emilia, Modena, Italy
3 Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Milano, Italy
Cerium oxide is widely employed as an active support for noble and transition metal
nanoparticles in environmental catalysis. Although the high efficiency, selectivity and stability
of cerium oxide based catalysts in several reactions have been largely demonstrated, the
atomic scale interaction mechanisms between cerium oxide and the metal nanoparticles are
still under discussion [1,2].
We present a study of a model system made of Ag nanoparticles supported on ceria ultrathin
films on Pt(111), aimed at getting more insight into the interaction mechanisms between the
Ag nanoparticles and the oxide surface. <strong>The</strong> cerium oxide films present wide flat terraces
and their stoichiometry can be modified in a controllable way [3]. Different amounts of Ag
have been deposited on cerium oxide films with different degree of reduction. <strong>The</strong>
morphology of the Ag nanoparticles and the preferential nucleation sites have been
investigated by scanning tunneling microscopy (Fig.1) and the results have been used to
interpret the information obtained by x-ray photoemission spectroscopy (XPS) on the
electronic properties of the system. A clear evidence for ceria reduction induced by Ag
nanoparticles has been observed. <strong>The</strong> experimental work has been complemented by first
principles density functional theory (DFT) calculations of Ag atoms and nanoparticles on
reduced and stoichiometric CeO2(111) surfaces. With the help of the DFT results the ceria
reduction has been ascribed to a net charge transfer from the Ag nanoparticles to the oxide.
<strong>The</strong> thermal stability of the Ag / cerium oxide system has also been investigated.
Fig.1: 100×100 nm 2 STM image of
0.07 Å Ag / 10 Å CeO2 / Pt(111).
Zoom: 9×7 nm 2 .
References
[1] J. A. Farmer, C. T. Campbell, Science, 329, 933 (2010).
[2] G. N. Vayssilov, Y. Lykhach, A. Migani, T. Staudt, G. P. Petrova, N. Tsud, T. Skala, A. Bruix, F.
Illas, K. C. Prince, V. Matolin, K. M. Neyman, J. Libuda, Nature Mater. 10, 310 (2011).
[3] P. Luches, F. Pagliuca, S. Valeri, J. Phys. Chem C 115, 10718 (2011).

Interactions of Rh, Pd, and RhxPdy (x, y = 4 or 6) on perfect and defective ceria
surfaces: Experimental and computational studies
YongMan Choi, a Morgan S. Scott, b and Hicham Idriss a, *
a Chemical Catalysis, Saudi Basic Industries Corporation (SABIC), P.O. Box 42503, Riyadh
11551, Saudi Arabia; ChoiY@SABIC.com; IdrissH@SABIC.com
b School of Chemical Sciences, <strong>The</strong> University of Auckland, Auckland 1142, New Zealand
Ceria-supported catalysts have attracted much interest due to their high reactivity for many
catalytic processes including the water gas shift reaction and reforming of hydrocarbons.
One of the main reasons is the fast oxygen transport making the oxidation reaction possible
and the ease by which Ce 4+ cations are reduced to Ce 3+ cations and therefore, making
reduction reactions possible. Most of catalytic processes on CeO2 involve the presence of a
metal, thus the interface of the metal-CeO2 is crucial for the understanding of the catalytic
reactions. In this work, we undertook spin-polarized density functional theory (DFT)
calculations with the GGA + U method (Ueff = 5.0 eV) to clarify the interactions of noble
metals (Pd and Rh) and their bimetals (RhxPdy; x, y = 4 or 6) on perfect and oxygen deficient
CeO2(111) surfaces. We found that Rh has a far stronger adsorption energy than Pd (–3.41
and –1.60 eV, respectively), while such energy in bimetallic systems depends upon their
ratio of Rh and Pd. To correctly rationalize our computational findings, we analyzed density
of states (DOS) and charge transfer. While DOS calculations clearly show that the metal-O
binding results in the hybrization of the d orbital of the cluster and O 2p, the Bader charge
analysis verify the charge transfer from clusters to ceria. Furthermore, we verified the validity
of the ceria-supported models by comparing them with the model proposed from
experimental findings of ethanol interactions on real catalytic surfaces. We present
estimated vibrational frequencies to interpret our experimental results. For example, the
predicted symmetric vibration mode of -CH3 for CH3CH2OH on pure ceria (θ = 0.5 ML) is in
good agreement with the experimental data (2942 cm -1 and 2936 cm -1 , respectively). In
addition, potential energy profiles for ethanol decomposition on ceria-supported models were
constructed by locating transition states using the nudged elastic band (NEB) calculation.

Effect of the TiO2 reduction state on the catalytic CO
oxidation on supported Pt7 clusters
Harald Brune
Institute of Condensed Matter Physics (IPMC), Ecole Polytechnique Fédérale de Lausanne
(EPFL),
Station 3, CH-1015 Lausanne
harald.brune@epfl.ch
We present our results revealing the influence of the substrate bulk reduction state on the
catalytic CO oxidation of Pt7 clusters on TiO2(110)-(1×1). While a slightly reduced titania
crystal gives rise to a high catalytic activity of the adsorbed metal clusters, a strongly
reduced one almost entirely quenches the CO oxidation. This is due to thermally activated
diffusion of Ti3+ interstitials from the bulk to the surface where they deplete the oxygen
adsorbed onto the clusters by spillover leading to the formation of surface TiOx (x ≃ 2)
structures. On the strongly reduced crystal, this reaction is more rapid than the CO oxidation.

Disclosing growth kinetics of metal nanoparticles through plasmonic
response: the case of Ag/�-Al2O3(0001)
R. Lazzari and Jacques Jupille
Institut des NanoSciences de Paris,
Université Pierre et Marie Curie-CNRS UMR7588, 4 Place Jussieu, 75252 Paris, France
<strong>The</strong> determination of size and shape of supported particles is an unavoidable step in the
understanding of the chemical or physical properties appearing at the nanoscale. For metals,
plasmonics offer a powerful and flexible tool to characterize at a glance the average
morphology in situ during growth. Its outcomes compare favorably with Grazing Incidence
Small Angle X-Ray scattering [1,2].
Fig: Morphology evolution from plasmon peak
analysis
<strong>The</strong> strength and sensitivity of this approach
will be illustrated through the study by Surface
Differential Reflectivity Spectroscopy of the
vapor deposition of silver on Al2O3(0001) at
various temperatures (190-675K). Changes in
size, shape and density were derived from the
optical response modeled in the framework of
surface susceptibilities by assuming that
supported clusters were in the form of
truncated spheres. <strong>The</strong> pivotal importance of
temperature dependence of the dielectric
constant and of plasmon absorption
broadening was demonstrated.
<strong>The</strong> methodology was validated through a critical comparison with the physics of crystalline
growth. <strong>The</strong> sticking coefficient is found close to one up to 575K before dropping at T≈675K.
<strong>The</strong> growth proceeds through a growth step at a nearly constant particle density followed by
particle coalescence. Sensitivity to nucleation is achieved in the low flux regime. Time
dependence exponents of size are consistent with this growth scenario but discard static
coalescence and may favor a process with mobile clusters above a critical size. <strong>The</strong>
Arrhenius dependence of the saturation density highlights a nucleation on defects at low
temperature (T ≤ 300K) and enhanced detraping above. For particles bigger than 10 nm in
size, values of contact angle and adhesion energy (�=127.5 ± 1° and 0.48 ± 0.02 J.m -2 )
nicely agree with tabulated data and theoretical calculations. <strong>The</strong> fine evolution of the
particle contact angle is assigned to a competition between surface stress, interface
adhesion and strain induced by lattice-mismatch.
Some perspectives of use of plasmonics in gas adsorption characterization will also be
given.
[1] R. Lazzari, G. Renaud, C. Revenant, J. Jupille, Y. Borensztein, Phys. Rev. B. 79, 125428 (2009)
[2] G. Renaud, R. Lazzari, F. Leroy, Surf. Sci. Rep. 64, 255-380 (2009)
[3] R. Lazzari and J. Jupille, Nanotechnology to appear
[4] R. Lazzari and J. Jupille, Phys. Rev. B submitted

Tuning the shape of gold particles by doping the oxide support
Xiang Shao, Niklas Nilius, Hans-Joachim Freund
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Thin oxide films have well-established advantages with respect to bulk oxides, especially
what their conductive character, their preparation and easy characterization concerns.
Moreover, they open up fascinating new possibilities to engineer the physical and chemical
properties of oxide systems. One of the most promising approaches is doping the oxide
support, which is a standard methodology in the field of semiconductors. By substituting
intrinsic lattice atoms with foreign species, new defect states can be created in the oxide
band gap, which in turn change the electronic structure, but also the adsorption and
chemical behavior of the host oxide.
By combing thin-film technology with common doping techniques, we have investigated the
effect of small dopant concentrations in oxide surfaces using mainly scanning tunneling
microscopy. We demonstrate, how small amounts of Mo inserted into a well prepared
CaO(001) film dramatically changes the growth behavior of gold. Whereas Au forms
compact 3D particles on the non-doped material, monolayer-high islands are observed upon
doping. This crossover in growth dimensionality is explained by a charge transfer from the
Mo impurities that act as electron-donors to the Au ad-metal having acceptor character. <strong>The</strong>
underlying mechanism has been confirmed with a recent high-level DFT study. In contrast,
doping with under-valent ions, such as Li, blocks the effect of charge transfer, as the Li
species produce holes in the oxide electronic structures that effectively trap the available
excess electrons. Li doping as well as Li/Mo co-doping therefore stabilizes the 3D
equilibrium shape of the Au ad-particles that is observed also in the non-doped case. Our
results shed light on fundamental effects related to doping, which might be relevant even for
some industrial catalysts that always contain small impurity levels as a consequence of their
fabrication procedure.

Alumina supported array of transition metal nanoparticles:
Size-dependent oxidation kinetics
S. Surnev, A. Chaudhury, L. Gragnaniello, T. Ma, and F.P. Netzer
Institute of Physics, Surface and Interface Physics,
Karl-Franzens University Graz, A-8010 GRAZ, Austria
G. Barcaro and A. Fortunelli
Molecular Modeling Laboratory, IPCF-CNR, I-56124 Pisa , Italy
Oxide supported metal nanoparticles (NP) often demonstrate size-dependent catalytic
properties, which are generally attributed to the presence of low coordination surface sites,
charge transfer between the support and the particles and spatial confinement effects [1].
Here we present results on the size-dependent oxidation of Ni and Co NP, supported on an
AlOx/Ni3Al(111) substrate. <strong>The</strong> ultrathin alumina film on Ni3Al(111) has been demonstrated to
be a particularly suitable template providing preferential nucleation centers for metal NP
growth with a very narrow size distribution [2-4], as illustrated in the STM image of Fig. 1a for
Ni NP: the average size can be varied and controlled by the amount of the metal deposited.
<strong>The</strong> metal NP have been exposed to oxygen under kinetic conditions which ensure a
morphology conserving oxidation, as evident from the STM image in Fig. 1b, following the
complete oxidation of the Ni NP to NiO. <strong>The</strong> oxidation kinetics of the Ni and Co NP has been
followed in detail by high-resolution x-ray photoelectron spectroscopy (HR-XPS) with use of
synchrotron radiation. We observe for both the Ni and Co NP that the oxidation kinetics is
strongly dependent of the particle size/coverage (Fig. 1c) with the intermediate-size (~ 3 nm)
NP displaying the highest oxidation rate. Whereas the drop of the oxidation rate at larger NP
sizes can be ascribed to the decrease of reactive low-coordination surface sites and the
oxygen diffusion kinetics, the slower oxidation kinetics of the smallest NP is an intriguing
result which will be discussed in the paper.
(a) (b)
(b)
Work supported by the ERC Advanced Grant SEPON
[1] M. Chen, W. Goodman, Acc. Chem. Res. 39,739 (2006)
[2] S. Degen, C. Becker, K. Wandelt, Faraday Disc. 125, 343 (2004)
[3] G. Hamm, C. Becker, C.R. Henry, Nanotechnology 17, 1943 (2006)
[4] M. Schmid, G. Kresse, A. Buchsbaum, E. Napetschnig, S. Gritschneder,
M. Reichling, P. Varga, Phys. Rev. Lett. 99, 196104 (2007)
Oxide Coverage (a.u.)
1.0
0.8
0.6
0.4
0.2
Co coverage (Å):
2.5 1.5 3.5
5.0
0.0
0 100 200 300 400 500
Oxygen expoure (L)
Fig. 1: STM images (200nmx200nm) taken before (a) and after (b) the oxidation of Ni NP
(average size ~ 3nm) on alumina/Ni3Al(111); (c) Evolution of the CoO coverage at different
(c)

"Thin oxide films: the expected and the unexpected"
Hans‐Joachim Freund
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft
Department of Chemical Physics
Faradayweg 4‐6, D‐14195 Berlin, Germany
freund@fhi‐berlin.mpg.de
Electronic properties of oxide films quickly converge towards those of the bulk material
when studied as a function of atomic layers. We have prepared a variety of oxide films
including chromia, niobia, haematite, wuestite, and magnetite.
In the case of MgO we have investigated properties as a function of thickness of the film
explicitly. In particular, the phononic responses of the film as well as its ability to control
charge transfer from the metallic substrate into adsorbates has been investigated. From
those observations concepts may be developed to understand the reactivity of thin oxide
films under ambient conditions. For thick MgO and CaO films representing the bulk material
doping of the films with transition metal and alkali metal atoms and its influence on surface
properties has been investigated.

Shape and structure of supported MgO(100) nano-islands:
role of the adhesion at the metal/oxide interface.
Jacek Goniakowski and Claudine Noguera
CNRS-UPMC, Institut des Nanosciences de Paris, UMR 7588,
Boîte Courrier 840, 4, place Jussieu, 75252 Paris Cedex 05, France
In the last decade, there have been intense efforts to synthesize ultra-thin oxide films or
nanoobjects on metal substrates. At small sizes, both structural and electronic properties of
such objects are strongly influenced by the interaction with the metal substrate. This raises
questions related to epitaxial growth, formation of Moiré patterns, presence of interfacial
dislocations, elastic relaxation at the interfaces and patterning by the metal substrate. We
will present results on structural properties of epitaxial metal-supported oxide nano-islands,
obtained in the generic case of MgO(100)/metal [1]. In order to account for complex,
substrate-induced, structural distortions of the several-thousands-of-atoms-large oxide
nanoislands,
we have used the recently developed semi-empirical Hartree-Fock approach, which
scales quasi-linearly with the system size. We will discuss the role of interface misfit
dislocations on the island stability, on their shape and their structural characteristics. We will
show how these properties evolve as a function of the adhesion strength at the metal/oxide
interface and of the lattice mismatch between the two materials. We will compare our results
to predictions of the Frenkel-Kontorova model and we will make a link with recent
experimental results on MgO deposits on Ag(100) and Mo(100).
[1] C. Noguera, J. Godet and J. Goniakowski : Phys. Rev. B 81, 155409 (2010)

V/Ti and Mo/Ti mixed oxide layers on TiO2(110)
H. Kuhlenbeck, O. Karslioglu, E.Primorac, M. Naschitzki, H.-J. Freund
Fritz Haber Institute of the Max Planck Society, Chemical Physics Department, 14195 Berlin,
Germany
Many heterogeneous catalysts are based on mixed oxides. Catalytic processes occurring on
such systems may involve the co-operative action of different constituents. Also, complex
oxidation/reduction processes at the surface as well as charge exchange between surface
and bulk may give rise to intricate reaction mechanisms with a complexity going beyond that
of single-metal oxides. In order to study such processes we have prepared V/Ti and Mo/Ti
mixed oxide layers on TiO2(110). Both types of layer are prepared by co-deposition of the
respective metals in an oxygen atmosphere at elevated temperature. In the case of the V/Ti
mixed oxide layer a Ta/Ti mixed oxide layer was introduced between the TiO2(110) substrate
and the overlayer in order to block the diffusion of vanadium into the substrate. For
vanadium as well as for molybdenum the oxidation state of the metal ions in the bulk of the
mixed oxide layers is dominated by 4+. Reduction induces the formation of V 3+ instead of
Ti 3+ in the case of the V/Ti mixed oxide whereas annealing in oxygen leads to the
agglomeration of V 5+ /Mo 6+ at the surface of the respective mixed oxide. <strong>The</strong> corresponding
oxide aggregates can be removed by annealing at temperatures above the sublimation
temperature of the respective oxide which represents a method to prepare a defined
concentration of Mo 6+ /V 5+ oxide aggregates at the surface. For vanadium different ordered
surface structures were observed which points towards the formation of ordered mixed
surface oxides whereas for the Mo/Ti mixed oxide no LEED pattern different from that of
TiO2(110) could be observed. For the latter case, IV-LEED measurements and STM show
that the surface layer consists of TiO2 and that Mo forms aggregates with Mo in an oxidation
state of 6+ at the surface. Methanol adsorption leads to O-H bond scission resulting in
adsorbed methoxy groups and hydrogen atoms. <strong>The</strong> Mo oxidation state changes from 6+ to
4+ with the concomitant occurrence of band bending to higher binding energy. We attribute
this to a charge transfer from sub-surface Ti 3+ ions into ethoxy groups at the surface and to
the bonding of hydrogen atoms to the MoOx aggregates at the surface.

Carboxylate interactions with model titania surfaces
Authors: David Grinter, Patrick Nickels, Thomas Woolcot, Abdulrahman O. Alyoubi,
Sulaiman N. Basahel, Abdullah Y. Obaid, Ahmed A. Al-Ghamdi, El-Sayed H. Al-Mossalamy,
Geoff Thornton
Abstract
<strong>The</strong> adsorption and behaviour of many different small molecules on rutile TiO2(110) have
been studied in an attempt to understand the reactivity of the surface and its defect sites.[1]
One important class of molecules are carboxylates, which have a number of practical
applications including the linking of dye molecules to titania surfaces within Grätzel type dyesensitised
solar cells.[2]
In this work,[3] scanning tunneling microscopy (STM) has been used to investigate the
adsorption of benzoic acid on the rutile TiO2(110)(1 x 1) and the reconstructed TiO2(110)(1 x
2) surfaces. Benzoic acid binds to both surfaces dissociatively via a bridging geometry to two
Ti5c sites. At a slightly elevated sample temperature during deposition onto the (110) (1 x 1)
surface, a well-ordered (2 x 1) overlayer was formed at saturated benzoate coverage. On the
reconstructed (110) (1 x 2) surface, benzoate was observed to adsorb between the (1 x 2)
strands leading to a (2 x 2) superstructure at higher coverage. Atomically resolved images at
low benzoate coverage are consistent with bonding to a Ti2O3 added-row type of the
TiO2(110)(1 x 2) reconstruction. Prolongation along the axis perpendicular to the rows in the
STM images indicate a rotation of the benzene ring of 90°, which is reasonably explained by
hydrogen bond interaction between terminating O-atoms on the surface and H-atoms of the
ring.
[1] Pang, C. L.; Lindsay, R.; Thornton, G. Chem. Soc. Rev. 2008, 37, 2328–2353.
[2] O’Regan, B.; Graetzel, M. Nature 1991, 353, 737–740.
[3] Grinter, D.C et al. In preparation

THEORY OF OXIDES DOPING. TOWARDS A RATIONAL DESIGN OF NEW
CATALYTIC MATERIALS
Gianfranco Pacchioni
Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca,
via Cozzi, 53 - 20125 Milano, Italy
gianfranco.pacchioni@unimib.it
Doping inorganic solids with impurity atoms is a very consolidated method to modify their
chemical and electronic properties. Often doping of oxides is based on trial-and-error
procedures, but modern electronic structure theory provides a powerful way to identify
dopants and their combinations that can result in new properties. Furthermore, theory helps
in the identification of useful concepts for the design of new materials. In this talk we review
some recent results based on DFT calculations with hybrid functionals on the role of doping
in oxides. <strong>The</strong> first example is related to doping and codoping WO3 for photocatalytic
applications. This material has a complex electronic structure which results in a strong
anisotropy of the properties of oxygen vacancies [1,2]. Doping WO3 with Hf, or codoping it
with Hf and F, leads to a shift of both valence and conduction bands that should result in an
improved activity in photoelectrochemical water splitting. <strong>The</strong> second example is related to
doping of oxide thin films. <strong>The</strong>se systems exhibit special properties in the ultra-thin regime
due to the possible occurrence of electron transfer processes. In pure metal-supported oxide
thin films this is related to electron tunneling from the metal states to acceptor levels of an
adsorbate [3]. <strong>The</strong> same effect can be obtained by doping with transition metal atoms
incorporated in the inner layers of an oxide thin film [4]. <strong>The</strong> implications for catalysis by
supported metal particles is discussed.
1) F. Wang, C. Di Valentin, G. Pacchioni, “Electronic and structural properties of WO3: a
systematic hybrid DFT study”, J. of Physical Chemistry C, 115, 8345-8353 (2011).
2) F. Yang, C. Di Valentin, G. Pacchioni, “Semiconductor-to-metal transition in WO3-x: Nature
of oxygen vacancy”, Physical Review B, 84, 073103/1-5 (2011).
3) L. Giordano, G. Pacchioni, “Oxide films at the nanoscale as new catalytic materials”,
Accounts of Chemical Research, in press (2011).
4) X. Shao, S. Prada, L. Giordano, G. Pacchioni, N. Nilius, H.-J.Freund, “Shape control of
metal adparticles via doping of the oxide support: An STM and DFT study”, Angewandte
Chemie Int. Ed., in press (2011).

Active oxygen species in CO oxidation on Au/TiO2(110) evidenced during in situ
photoemission analysis
K. Dumbuya 1 , G. Cabailh 2 , R. Lazzari 2 , J. Jupille 2 , L. Ringel 1 , M. Pistor 1 , O. Lytken 1 ,
H.-P. Steinrück 1 , J. M. Gottfried 1
1
Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3,
91058 Erlangen, Germany
2
Institut de Nanosciences de Paris, Université Pierre et Marie Curie and CNRS, 4 Place
Jussieu,
75252 Paris, France
Numerous experiments were dedicated to the search for the active site in the CO oxidation
over supported gold catalysts. In situ photoelectron spectroscopy (in situ XPS), which allows
analysis in reactive conditions, is a powerful technique in this regard. On Au/TiO2(110),
Willneff et al. [1] observed Au 4f core-level shifts of +0.3 and +0.9 eV, which they assigned
to bulk-like metallic gold and to intermediate gold species, respectively; similar +0.3-0.4 eV
shifts were recorded by Herranz et al. [2]; Jiang et al. reported a very different shift of +2.3
eV [3], which was explained by photoelectron induced dissociative chemisorption of oxygen.
To revisit these conflicting results that question the applicability of in situ XPS to characterize
the catalytic reaction itself, Au/TiO2(110) model catalysts were analyzed by in situ XPS in the
presence of O2, CO and CO + O2 mixture in the 0.1–1 mbar range. Two different samples
were prepared, with particles close to the optimum size for the catalytic oxidation of CO (~ 2
nm) [4], and larger than that size (~3 nm). Two distinct Au 4f shifts were observed during the
same experiment [5]: - a +0.9 eV shift, whose origin is controversial (Au (I) oxide versus final
state effects) is most likely due to final state effects; - under an oxygen pressure of 1 mbar, a
new component shifted by +2.4 eV evolved at all particle sizes. <strong>The</strong> activation was much
more efficient on the 2 nm particles than on the 3 nm particles. Absent in 0.1 mbar O2,
consistently with Wilneff et al. [1] and Herranz et al. [2], the +2.4 eV Au 4f shift appeared in 1
mbar O2 as seen by Jiang et al. [3]. It was attributed to a photoinduced activation of oxygen
and a further oxidation of gold. Photons are required since XPS performed in vacuum after
transfer of a Au/TiO2(110) sample exposed to 20 mbar O2 only evidenced ~ + 0.5 eV Au 4f
shift. But, although experiments at Lawrence Berkeley National Laboratory [2,3] involved a
photon flux (4×10 14 photons×cm -2 ×s -1 ) 5 orders of magnitude higher than that used in the
present work, they show the same pressure-dependent activation of oxygen as herein.
<strong>The</strong>refore, the intensity of the + 2.4 eV Au 4f shift only depends on the oxygen coverage
(equivalent to pressure since all experiments were done at the same temperature (300 K)) in
the photon flux range which was explored. Such an occurrence of a pressure-dependent
activation reconciles previously conflicting XPS data [2,3].
Finally, the rapid disappearance of the +2.4 eV Au 4f component in a 1:1 mixture of CO and
O2 demonstrated the high reactivity of the activated oxygen species toward CO. Rates of
evolution and consumption of this component were found to be higher for the particles close
to the optimum size for the catalytic oxidation of CO.
[1] E. A. Willneff et al., J. Am. Chem. Soc. 128 (2006) 12052.
[2] T. Herranz et al., Catalysis Today 143 (2009) 158.
[3] P. Jiang et al., J. Am. Chem. Soc. 132 (2010) 2858.
[4] I. Laoufi et al., J. Phys. Chem. C 115 (2011) 4673.
[5] K. Dumbuya, G. Cabailh, R. Lazzari, J. Jupille, L. Ringel, M. Pistor, O. Lytken, H.-P. Steinrück,
J. M. Gottfried, Catalysis Today, to appear.

Structure and Reactivity of Steps on Rutile TiO2(110)
Umberto Martinez,¤ and Lasse B. Vilhelmsen, Henrik H. Kristoffersen,
Jess Stausholm-Møller and Bjørk Hammer
Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy,
Aarhus University, DK-8000 Aarhus C, Denmark
Abstract
Titanium dioxide and its properties have attracted much attention due to the wide range of
catalytic and photocatalytic applications. Rutile TiO2(110) surface is considered an important
model system for metal oxide surfaces. <strong>The</strong> activity of this surface has been extensively
studied both experimentally and theoretically with focus on surface point defects such as
bridging oxygen vacancies (VO), hydroxyl groups (OHbr) or Ti interstitials in the near surface
region. Although step edges are always present at typical experimental conditions, very little
is known about their properties and their influence on the reactivity of this surface. In
particular, systematic theoretical studies have never been reported before.
We present the first detailed investigation of the structure and reactivity of monoatomic steps
on (1×1)–TiO2(110). Specifically, the two most stable h001i and h1¯11i and the less stable
h1¯10i step edges are considered. Employing an automated genetic algorithm that samples
a large number of candidates for each step edge, more stable, reconstructed structures were
found for the h1¯11i and h1¯10i step edges, while the bulk truncated structures were
recovered for the h001i step edge. We also demonstrate that reconstructed step edges are
easily reducible, with important consequences in the reactivity of the TiO2(110) surface. <strong>The</strong>
interaction of reduced step edges with small molecules, namely water and alcohols, is
discussed. Our findings are in agreement with previous experimental results. Implications for
some new and interesting phenomena occurring at this oxide surface are discussed.

Surface properties and reactivity of TiO2 nanocrystals: a combined
experimental and ab initio study
Lorenzo Mino, Anna Maria Ferrari, Giuseppe Spoto, Silvia Bordiga, Adriano Zecchina
Department of Inorganic, Physical and Materials Chemistry nd NIS Centre of Excellence,
University of Turin, via P. Giuria
7, 10125 Torino, Italy
Titanium dioxide is one of the most important metal oxides because of its applications as
white pigment, as important component in solar cells and as photocatalyst [1]. In the last two
applications the relevant phenomena are occurring at the surface of anatase nanoparticles,
which are generally considered to be more active than rutile ones [2]. <strong>The</strong>refore it is relevant
for both technological and fundamental motivations to study the structure of the different
surfaces terminating the anatase nanocrystals. In our work [3] we performed periodic DFT
calculations of the structure of (101), (100), (001) and (112) anatase faces and of the
vibrational properties of CO adsorbed on them at two coverages. Comparison of these
results with HRTEM images of the adsorbing nanocrystals of P25 (a highly crystalline TiO2
characterized by outstanding photocatalytic properties and well shaped crystals) and with
the experimental FTIR spectra of adsorbed CO on them at 60K (Figure 1) allowed to
assign with unprecedented precision the complex spectrum of CO. <strong>The</strong> relevance of this
achievement can be briefly described as follows. CO is a weak Lewis base and its stretching
frequency changes when the molecule interact with the surface Ti4+ sites since the greater
is the electrophilicity of the metal cation, the higher is the blue shift with respect to the value
in gas phase [4]. As the electrophylic character of Ti4+ sites depends upon the face, the
FTIR spectrum of adsorbed CO is composed by several peaks, each one corresponding to a
specific facelet. On this basis it is evident that the IR spectrum give information about
nanocrystals morphology and about the reactivity of different faces. To test the reactivity
aspect, the water and acetylene adsorption has been studied. It is shown that the different
faces are characterized by different reactivity. Acetylene is a special probe of the surface
properties. In fact, unlike CO, it has acidic character and hence is able to probe the basic
O2- ions present on the different faces. It is shown that acetylene is irreversibly interacting
with basic sites with formation of colored oligomeric species. This reaction seems to be
particularly interesting since these in situ grown acetylene polymers can act as potential
sensitizers to improve the visible light photoactivity of TiO2.
CO adsorbed at different coverages on highly
dehydroxylated Degussa P25 nanocrystals.
Figure 1. Band assignment in FTIR spectra of
[1] A. Fujishima, X. T. Zhang, D. A. Tryk, Surf. Sci. Rep., 63, 2008, 515-582.
[2] U. Diebold, Surf. Sci. Rep., 48, 2003, 53-229.
[3] L. Mino, A. M. Ferrari, V. Lacivita, G. Spoto, S. Bordiga, A. Zecchina, J. Phys. Chem. C, 115,
2011, 7694-7700.
[4] K. I. Hadjiivanov, D. G. Klissurski, Chem. Soc. Rev., 25, 1996, 61-69

Toward Surface Science of Metal Oxide Photocatalysts
Hiroshi Onishi
Chemistry Department, Kobe University, Japan
http://www.edu.kobe-u.ac.jp/sci-onishi/index-E.html, oni@kobe-u.ac.jp
<strong>The</strong>re is rising interest in producing CO2-free sources of energy. <strong>The</strong> photocatalytic splitting
reaction of water is one of the promising processes when driven by solar light. Efforts have
been made to prepare efficient photocatalysts. Doping with hetero-elements provides a
common and efficient way to enhance the rate of H2 production. It is important to know how
the dopants positively affect catalytic performances. We have been studying photoexcited
dynamics of metal oxide photocatalysts using time-resolved infrared (IR) absorption
spectroscopy [1, 2]. Electrons are excited in a photocatalyst by pulsed light irradiation. <strong>The</strong>
excited electrons exhibit the absorption of mid-IR light. <strong>The</strong> decay of the IR absorbance is
related to the kinetics of electron-hole recombination in the bulk and electron-consuming
reactions at the surface. In the current talk, extensions of this study to doped TiO2 [3] and
doped NaTaO3 [4, 5] are reviewed to stress a demand for developing the surface science of
photocatalysts. In particular, the rate of electron-hole recombination is quantitatively
compared with the steady-state rate of H2 production on doped NaTaO3. <strong>The</strong> efficiency of
the electron-to-H2 conversion is related to the nanometer-scale topography of the doped
photocatalyst surfaces. Our primary efforts [6, 7] to respond the demand using scanning
probe microscopy are also mentioned.
[1] A. Yamakata, T. Ishibashi, K. Takeshita, H. Onishi, Topics in Catalysis 35 (2005) 211.
[2] A. Yamakata, T. Ishibashi, H. Onishi, J. Mol. Cat. A 199 (2003) 85.
[3] T. Ikeda, T. Nomoto, K. Eda, Y. Mizutani, H. Kato, A. Kudo, H. Onishi, J. Phys. Chem. C
112 (2008) 1167.
[4] M. Maruyama, A. Iwase, H. Kato, A. Kudo, H. Onishi, J. Phys. Chem. C 113 (2009)
13918.
[5] A. Yamakata, T. Ishibashi, H. Kato, A. Kudo, H. Onishi, J. Phys. Chem. B 107 (2003)
14383.
[6] A. Sasahara, K. Hiehata, H. Onishi, Catalysis Surveys from Asia 13 (2009) 9.
[7] R. Bechstein, M. Kitta, J. Schütte, A. Kühnle, H. Onishi, J. Phys. Chem. C 113 (2009)

Photocatalysis on oxides:
Case studies on rutile and anatase TiO2 single crystals surfaces
Christof Wöll
Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT)
76131 Karlsruhe, FRG
Photo-induced chemical reactions at surfaces of wide bandgap semiconductors like TiO2 are
important because they are central to many promising applications related to energy
conversion and other associated processes with environmental impact. In addition, because
photo-catalytic reactions are largely non-activated processes depending only weakly on
temperature the study of such reactions is relevant to understand fundamental processes
occurring on dust particles in the earth’s atmosphere as well as in space. Experimental data
for photoinduced reactions on well-defined metal oxide single crystal surfaces, which would
also provide the basis for a more thorough theoretical understanding, are scarce – in
contrast to powder materials for which a rather large set of experimental data exists. <strong>The</strong>
main reason for this unfortunate lack of information for well-defined single crystals is the fact
that spectroscopic techniques not involving electronic excitations have – due to technical
difficulties – not been applied for studying photo-induced reactions on such model
substrates. <strong>The</strong> technical difficulties result from the fact that the IR-intensity of adsorbate
vibrational modes on oxide surfaces is about an order of magnitude weaker than for metal
single crystals.
We have designed a new apparatus, which combines a state-of-the-art FT-IR spectrometer
with a dedicated UHV-chamber [1] to monitor the adsorption and reaction of CO over
TiO2(110) single crystals using reflection–absorption infrared spectroscopy (RAIRS).
Here we will report on the first IR studies of CO-adsorption on TiO2 single crystal surfaces
and its photo-oxidation. <strong>The</strong> success of our experiment [2] may open a new era in vibrational
spectroscopy on single crystal metal oxide surfaces. In addition to the experimental results
on rutile TiO2 we will discuss recent measurements for anatase TiO2, where the photocrosssection
of CO photooxidation was found to be an order of magnitude larger than for rutile [3].
[1] Y.Wang, A.Glenz, M. Muhler, Ch. Wöll, Rev. Scient. Instr. 80, 113108 (2009)
[2] Ch. Rohmann, Y. Wang, M. Muhler, J. B. Metson, H. Idriss, Ch. Wöll, Chem. Phys. Lett.
460, 10 (2008)
[3] M. Xu, Y. Gao, E. Martinez Moreno, M. Kunst, M. Muhler, Y. Wang, H. Idriss, C. Wöll,
Phys. Rev. Lett. 106, 138302 (2011)

Local Environment of Ti 3+ Ions in Reduced TiO2 Through
Spin Density Studies.
Mario Chiesa, Stefano Livraghi, Maria Cristina Paganini, Sara Maurelli, Elio Giamello
University of Torino, Dept. Chimica IFM, Via Giuria 7, 10125-Torino
E-mail: m.chiesa@unito.it
Following the fate of excess electrons in oxide semiconductors is crucial in order to
understand and harness the properties of these materials for a variety of challenging
applications spanning from catalysis to light-harvesting, and gas sensing. Titanium dioxide
(TiO2), is among other semiconducting oxides, one of the most studied systems and can be
considered as a model substrate to investigate phenomena concerned with excess charge
generation and transport. 1 Key to the applications of this oxide in different areas are in fact
excess electrons associated with intra band gap defective states, induced by reductive
treatments or n-type doping with aliovalent elements (e.g. Nb or F). Despite the importance
of these defective states in determining the physical and chemical properties of TiO2 , the
very nature of these states and the associated degree of charge localization, remain poorly
understood and are currently at the centre of a lively scientific debate. 2-5
Electron Paramagnetic Resonance (EPR) spectroscopy is one of the most potent techniques
to investigate the microscopic nature of paramagnetic defects in solids. As part of a
systematic study of the nature of reduced states in TiO2, we have synthesized differently ndoped
TiO2 polycrystalline samples (rutile and anatase) enriched in 17 O (I=5/2) and
performed EPR and Hyperfine Sublevel Correlation (HYSCORE) studies to investigate the
hyperfine interaction between Ti 3+ ions and lattice coordinated oxygens. 6
Different EPR signals are observed depending on the doping method and on the
investigated polymorph (rutile or anatase) which, are characterized by specific 17 O hyperfine
couplings. <strong>The</strong>se data allow monitoring for the first time the spin density delocalization over
the first shell of oxygen ligands for the different defects revaling a different degree of the
unpaired electron wave function for the different cases.
1) U. Diebold, Surf. Sci. Rep. 2003, 48, 53.
2) S. Wendt, P. T. Sprunger, E. Lira, G. K. H. Madsen, Z. Li, J. Ø. Hansen, J. Matthiesen, A.
Blekinge-Rasmussen, E. Lægsgaard, B. Hammer, F. Besenbacher Science 2008, 320, 1755.
3) C. Di Valentin, G. Pacchioni, A. Selloni, J. Phys. Chem. C 2009, 113, 20543.
4) C. M. Yim, C. L. Pang, G. Thornton, Phys. Rev. Lett. 2010, 104, 036806.
5) P. Kruger, S. Bourgeois, B. Domenichini, H. Magnan, D. Chandesris, P. Le Fevre, A. M.
Flank, J. Jupille, L. Floreano, A. Cossaro, A.Verdini, A. Morgante Phys. Rev. Lett. 2008, 100,
055501
6) S. Livraghi, S. Maurelli, M.C. Paganini, M. Chiesa, E. Giamello Angew. Chem. Int. Ed. 2011,
50, 8038.

Photoactivity of TiO2 rutile and anatase surfaces
Mingchun Xu1, Heshmat Noei1, Youkun Gao1, Marinus Kunat2, Hicham Idriss3,
Christof Wöll4, Martin Muhler1, and Yuemin Wang1
1 Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44801 Bochum,
Germany
2Hahn-Meitner-Institut, Glienicker Strasse 100, D-1000 Berlin 39, Germany
3Department of Chemistry, University of Aberdeen and School of Engineering, Robert
Gordon University, UK
4Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), 76021
Karlsruhe, Germany
<strong>The</strong> photochemistry on semiconductor TiO2 surfaces has recently received enormous
attention
from both fundamental and technological perspectives because of its applications in the
fields
of solar energy conversion, water splitting, environmental treatments, etc [1]. In spite of
extensive studies, major issues concerning the photoactivity of this important oxide are still
under debate. <strong>The</strong> reasons behind the differences in activity between the two most important
polymorphs of titania, rutile and anatase, are still not resolved. Here we report the first
infrared (IR) study of photoreactions of CO and some organic molecules on TiO2 anatase
and
rutile surfaces using a novel ultrahigh vacuum (UHV) FTIRS apparatus [2]. <strong>The</strong> high-quality
RAIRS data will provide detailed insight into photocatalytic activity and reaction mechanisms
on TiO2 surfaces. It was found that the anatase (101) surface exhibits a substantially higher
activity for CO photooxidation than the rutile (110) surface. This surprisingly large difference
in activity tracks the bulk electron-hole pair life time difference for the two TiO2
modifications. In addition, we will present vibrational spectroscopic study of doping effects
on metal oxide photocatalysts [3,4].
References
[1] T. L. Thompson and J. T. Yates, Jr., Chem. Rev. 106, 4428 (2006).
[2] M. Xu, Y. Gao, E. M. Moreno, M. Kunat, M. Muhler, Y. Wang, H. Idriss, Ch. Wöll,
Phys. Rev. Lett. 106, 138302 (2011).
[3] M. Xu, Y. Gao, Y. Wang, Ch. Wöll, PCCP 12, 3649 (2010).
[4] H. Qiu, F. Gallino, C. Di Valentin, Y. Wang, Phys. Rev. Lett. 106, 066401 (2011).

Preparation, Characterization, and Catalytic Activity of Model WO3 and MoO3 Catalysts
Zdenek Dohnalek
Pacific Northwest National Laboratory
Supported early transition metal oxides (TMO) have important applications in numerous
catalytic reactions. In our studies, dehydration and partial oxidation of alcohols are employed
to probe the catalytic activity of WO3 and MoO3. To understand how TMO structure and
binding affect catalytic properties we prepared a number of well-characterized model
systems. Direct sublimation of WO3 and MoO3 solids was used to generate cyclic gas-phase
(WO3)n and (MoO3)n clusters. As shown in our matrix isolation experiments sublimation leads
to pure (WO3)3 clusters, but results in a range of (MoO3)n cluster sizes (n = 3-6). <strong>The</strong> oxide
clusters of both metals were embedded in alcohol matrices and their support-free chemistry
was explored in subsequent temperature programmed reaction experiments. Model
supported catalysts were created by depositing (WO3)3 clusters on TiO2(110) and FeO(111)
and subsequently characterized using scanning tunneling microscopy and surface sensitive
spectroscopies. In other studies, epitaxial and nanoporous thin WO3 films were prepared on
Pt(111). <strong>The</strong> catalytic chemistry of all the systems is compared and contrasted with that
observed on unsupported (WO3)3 clusters. Calculations employing Density Functional
<strong>The</strong>ory (DFT) provide molecular-level mechanistic insight into the role structure and binding
of (WO3)3 clusters to the support plays in determining their catalytic properties.

<strong>The</strong> Phase Stability of LaMnO3 and its Surfaces:
A Hybrid Density Functional Study
of an Alkaline Fuel Cell Catalyst.
E. A. Ahmad12, D. Kramer13, L. Liborio12, G.Mallia12, A. R. Kucernak1 and N. M.
Harrison1,2,4*
1Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ,
UK
2Thomas Young Centre, Imperial College London,
South Kensington, London SW7 2AZ, UK
3Faculty of Engineering and the Environment ,
University of Southampton, University Road, Southampton SO17 1BJ, UK
4Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, UK
(Dated: September 30, 2011)
Abstract
<strong>The</strong> phase stability of low temperature LaMnO3 and its surfaces is studied using hybridexchange
density functional theory (DFT) in CRYSTAL09. <strong>The</strong> underpinning DFT total
energy calculations are embedded in a thermodynamic framework that takes optimal
advantage of error cancellation within DFT. It has been been found that by using the ab initio
thermodynamic techniques de-scribed here, the standard Gibbs formation energies of the
series of Mn oxides can be calculated to a significantly greater accuracy than was previously
reported (a mean error of 1.6% with a maximum individual error of -3.0%). This is attributed
to both the methodology for isolating the chemical potentials of the reference states, as well
as the use of the B3LYP functional to thoroughly inves-tigate the ground state energetics of
the competing oxides. By adopting this approach, stability of the low index LaMnO3 surfaces
was also investigated. PACS numbers: 31.15.A- 65. 81.30.-t 88.30.ph
Electronic address: ehsan.ahmad08@imperial.ac.uk

Chi YIM – IWOX Abstract
<strong>The</strong> growth of Pd islands on rutile TiO2(110)-(1×1) and CO adsorption on top of those
islands were investigated using synchrotron light spectroscopies and scanning tunneling
microscopy. <strong>The</strong> Pd islands, which were grown by physical vapour deposition (PVD) of Pd
onto the TiO2(110) surface at T ~ 800 K, had a pseudo-hexagonal shape, with an average
diameter of 30 nm and height of 5 nm, and were not encapsulated with Ti n+ (n

DFT study of the electronic structure of F-doped titania
Sergio Tosoni, 1,2 Oriol Lamiel-Garcia, 1 Daniel Fernandez-Hevia, 2,3 Jesús Perez Peña, 2 Francesc Illas 1
1) Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB),
Universitat de Barcelona, C/ Martí i Franquès 1, E-08028 Barcelona, Spain
2) Departamento de Química, Universidad de Las Palmas de Gran Canaria, Campus Universitario de
Tafira, 35017 Las Palmas de Gran Canaria, Spain
3) INAEL Electrical Systems S.A., C/ Jarama, 5, 45007 Toledo, Spain
<strong>The</strong> photocatalytic properties of titania, even though known since a long time, are now an object of
growing interest both for fundamental research and industrial applications. In particular, growing
efforts are dedicated to look at viable strategies to reduce the wide band gap of titania, in order to
improve its activity under sunlight irradiation.
P-doping is an interesting possibility to reduce the band gap by introducing populated states above
the valence band of a semiconductor. A remarkable number of studies has been dedicated to Ndoping
in different phases of titania. Far less is known about the effect of F-doping, even though some
experiments prove that F-doped TiO2 has interesting properties for photovoltaic and photocatalytic
applications.
Aim of the present work is to study the electronic structure of F-doped titania by means of density
functional calculations. Mimicking the conditions of hydrothermal synthesis of titania nanoparticles,
which expose the samples to high temperature and pressure, we include in the study all the solid
polimorphs of TiO2: anatase, rutile and brookite. Attention is then dedicated to fluorine doping on the
anatase (001) and rutile (110) surfaces, because these have been experimentally identified as stable
and highly reactive.
Among many different DFT approaches, we have found that the PBE functional corrected with an
empirical Hubbard’s parameter (PBE+U) represents a good compromise between accuracy and
demand of computer power.
We conclude that F-doping remarkably reduces the band gap of titania, inducing interesting effects in
terms of reactivity.

Reactivity vs. Morphology – Steps on TiO2(110)
R. Bechstein, F. Rieboldt, S. Wendt, E. Lægsgaard, and F. Besenbacher
Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy,
Aarhus University, DK-8000 Aarhus C, Denmark
<strong>The</strong> promising applications of TiO2-based materials have spurred tremendous research both
in fundamental as well as in more applied research fields. However, in surface science
studies particularly flat rutile TiO2(110)-(1×1) has been investigated intensely, whereas step
edges and kink sites have often been ignored so far.
In applications such as photocatalysis, photodegradation of organic pollutants and the
photo-generation of hydrophilic films the interaction of O2 with TiO2 plays an important role.
In recent years the oxygen chemistry occurring on flat TiO2(110) surfaces has been
understood in great detail and the role of bulk and surface defects has been unravelled [1-5].
However, the role of step edges in this important interaction is today still unexplored.
Generally, the presence of step edges and kink sites is considered to be beneficial for
surface catalysed reactions. On the surface of rutile TiO2(110) single crystals two distinct
types of stable step edges exist, namely and steps [6]. By means of STM,
TPD and UPS experiments we have studied TiO2(110) surfaces characterized by different
densities of and steps. We show that differences in reducibility and reactivity
can be traced back to the prevailing step edges present on the surface, as exemplified for
the interaction of O2 with miss-cut TiO2 crystals.
Fig. 1. STM images of a TiO2(110) surface with a miss-cut angle of ~5° in [001]
direction. A high density of step edges is created whereas steps
do not occur. An intrinsic property of this surface is the presence of linear adstructures.
[1] S. Wendt, P. T. Sprunger, E. Lira et al., Science 320, 1755 (2008).
[2] E. Lira, J.Ø. Hansen, P. Huo et al., Surf. Sci. 604, 1945 (2010).
[3] Z.-T. Wang, Y. Du, Z. Dohnálek, I. Lyubinetsky, J. Phys. Chem. Lett. 1, 3524 (2010).
[4] S. Tan, Y. Ji, Y. Zhao et al., J. Am. Chem. Soc. 133, 2002 (2011).
[5] E. Lira, S. Wendt, P. Huo et al., J. Am. Chem. Soc. 133, 6529 (2011).
[6]U. Diebold, J. Lehman, T. Mahmoud et al., Surf. Sci. 411, 137 (1998).

Direct imaging of Pt atoms on TiO2 (110) surface by aberration corrected
scanning transmission electron microscopy
Teng-Yuan Chang 1 , Ryo Ishikawa 1 , Naoya Shibata 1 , Katsuyuki Matsunaga 2 , Yukio Sato 1 ,
Teruyasu Mizoguchi 3 , Takahisa Yamamoto 4 , Yuichi Ikuhara 1
1 Institute of Engineering Innovation, the University of Tokyo
2 Department of Materials Science and Engineering, Nagoya University
3 Institute of Industrial Science, the University of Tokyo
4 Department of Advanced Materials Science, the University of Tokyo
chang@sigma.t.u-tokyo.ac.jp
Pt dispersed on TiO2, one of the most active catalysts for CO oxidation and photocatalysts,
as well as a typical system for the strong-metal-support-interaction (SMSI) phenomenon, has
recently attracted much attention. To fully understand the emergence of its properties, it is
necessary to know the exact adsorption sites of Pt atoms on TiO2 surface at the beginning of
the growth of a Pt nanocluster – a very early stage when first one or two Pt atoms coming to
the TiO2 surface [1]. Some density-functional theory (DFT) calculations have revealed the
adsorption and migration profile of single neutral Pt atoms on the stoichiometric and reduced
rutile TiO2 (110) surface [2-3]. However, detailed experimental estimation, especially in the
case of Pt dimers, is still scarce because direct observation of such small amount of atoms is
extremely difficult. Thankfully, a recent advancement of aberration corrector has propelled
the capabilities of the scanning transmission electron microscope (STEM) to a whole new
level of sensitivity, leading us to visualize single atoms with unprecedented detail [4].
Aberration corrected high-angle annular dark-field STEM (HAADF-STEM), with its image
intensity strongly dependent on the atomic number Z, was used to study the interface
structure of Pt/TiO2 (110), which was prepared by evaporating pure Pt onto a thin TiO2 (110)
TEM specimen. We found by a plan-view high-resolution HAADF-STEM image of a TiO2
(110)-supported Pt single atom, showing that a Pt single atom finds its most favorable
position on the bridging oxygen vacancy site on the reduced TiO2 (110) surface, which is in
agreement with other theoretical studies [2-3]. Also, our technique help us clearly image Pt
dimers on the TiO2 (110) surface. We believe that aberration corrected STEM will be a very
powerful technique to image the single atoms or nanoclusters on the surface of oxides.
Reference
[1] J. Barth et al., Nature, 437, 671, 2005
[2] H. Iddir et al., Phys. Rev. B, 72, 081407(R), 2005
[3] V. Celik et al., Phys. Rev. B, 82, 205113, 2010
[4] A. Herzing et al., Science, 654, 1331, 2008

Ab initio study of Anatase TiO2 surfaces for nanoparticle modelling in solar
hydrogen production.
by Authors : F. Sanches a , L. Liborio a G. Mallia a , and N. Harrison a,b
a, Chemistry Department - Thomas Young Centre, Imperial College London , London, UK.
b, STFC, Daresbury Laboratory, Daresbury, Warrington, UK.
Abstract :
Photolytic water splitting as a method of hydrogen production has attracted a lot of attention
since Honda et al first demonstrated this concept with TiO2 in 1972 [1]. TiO2 has since been
used as a reference material in numerous experimental as well as theoretical studies in the
field of solar hydrogen production[2][3][4]. <strong>The</strong> aim of this work is to study anatase TiO2
surfaces with the aim of creating a model of a TiO2 nanoparticle. To achieve this, we use
hybrid density functional theory. We study low-index and vicinal surfaces to gain an insight
into the energetics and electronic properties at the nanoscale. <strong>The</strong> results shown here help
in the understanding of the composition of (anatase) TiO2 nanocrystals (and could be
extended to nanocrystalline films), thus providing knowledge fundamental to the
comprehension of the interactions between TiO2 and water during water photolysis.
References
1. Fujishima K. and Honda, A. Nature, 1972 238, 37.
2. Graetzel, M. Nature, 2001, 414, 338-344
3. Lazzeri, M. and Selloni, A. Phys. Rev.Lett. 2001, 87, 266105
4. Labat, F., Baraneka, P. Domain, C., Minot, C., Adamo, C. J. Chem. Phys. 2007 126,
154703

Direct Evidence of Ethanol Dissociation on Rutile TiO2(110)
S. Wendt, J. Ø. Hansen, P. Huo, U. Martinez, E. Lira, Y.Y. Wei, R. Streber,
E. Lægsgaard, B. Hammer, and F. Besenbacher
Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy,
Aarhus University, DK-8000 Aarhus C, Denmark
Key words: TiO2(110), ethanol, point defects, STM
Abstract
Intrinsic point defects on sputtered and vacuum-annealed rutile TiO2(110)-(1 × 1) will be
introduced by a summary of representative scanning tunnelling microscopy (STM) images
and STM movies, i.e. time-lapsed STM imaging [1,2]. Subsequently, the interaction of
ethanol with reduced TiO2(110) will be addressed (Fig. 1). <strong>The</strong> STM measurements reveal
the coexistence of molecularly and dissociatively adsorbed ethanol species on surface Ti
sites [3]. In addition, direct evidence for ethanol dissociation at bridging O vacancies (Obr
vac.) will be presented. Accompanying density functional theory (DFT) calculations support
the assignments made in the STM studies and rationalize the observed distinct diffusion
behaviors of molecularly and dissociatively adsorbed ethanol species [3]. Finally, the
thermally and photo-stimulated reactions of the adsorbed ethanol species will be discussed.
Fig. 1. (a) – (f) Selected Snapshots from an STM movie recorded at 191 K, revealing the
diffusion of ethanol molecules and the formation of strongly bound ethoxides at Obr vac.
sites. (g) STM line profiles of identified ethanol adsorbates on reduced TiO2(110).
[1] S. Wendt, P. T. Sprunger, E. Lira, G. K. H. Madsen, Z. Li, J. Ø. Hansen, J. Matthiesen, A.
Blekinge-Rasmussen, E. Lægsgaard, B. Hammer, F. Besenbacher, Science 320, 1755 (2008).
[2] S. Wendt, J. Matthiesen, R. Schaub, E. K. Vestergaard, E. Lægsgaard, F. Besenbacher, B.
Hammer, Phys. Rev. Lett. 96, 066107 (2006).
[3] J. Ø. Hansen, P. Huo, U. Martinez, E. Lira, Y.Y. Wei, R. Streber, E. Lægsgaard, B. Hammer, S.
Wendt, F. Besenbacher, Phys. Rev. Lett. 107, 136102 (2011).

Poster Session 1
Surface EXAFS characterization of Mo(Ni) model catalysts
supported on alumina single crystals.
Asma Tougerti, Michel Che and Xavier Carrier
1 UPMC (Univ. P. et M. Curie) & CNRS, Laboratoire de Réactivité de Surface, Paris, France
Introduction
A rational design of oxide-supported catalysts requires the fundamental description of the adsorption
of transition metal ions on oxide surfaces. However this objective is made difficult by the ill-defined
surface structure of most oxide supports which are often non-crystalline with a high surface area
exposing different surfaces with ill-defined sorption sites. <strong>The</strong> sorption system may be simplified by
using oriented oxide single crystals that have a limited number of well-defined surface sites. This
reductionist approach applied to aqueous deposition is seldom used in the field of heterogeneous
catalyst preparation where most of the model studies use surface science deposition techniques (e.g.
CVD). In the present work, Mo(Ni) precursors are deposited on model a-alumina single crystal wafers
in aqueous phase in order to mimic conventional heterogeneous catalysts preparation on powder
oxide supports. Surface-EXAFS (in Grazing-Incidence geometry) is used to gain molecular scale
understanding of individual sorption sites and metal speciation.
Experimental
Mo(Ni)-based model catalysts have been prepared by aqueous phase deposition of Mo VI
((NH4)6Mo7O24) and Ni II (Ni(NO3)2) on α-Al2O3 single crystals wafers with two orientations: (0001) and
(11 02). Characterization was performed with Grazing-incidence EXAFS (GI-EXAFS) at the ESRF
(Fame and Gilda) and at SOLEIL (Diffabs). DFT calculations 1 were applied to give new insight into the
surface structure of both α-Al2O3 orientations in relevant experimental temperature and pressure
ranges
Results/Discussion
Using a periodic DFT approach coupled to a thermodynamic model, we have determined the stability
of the (0001) and (11 02) orientations of the model α-Al2O3 support as a function of water coverage
and to identify the different exposed surface sites. <strong>The</strong> (11 02) orientation is terminated with singly
coordinated hydroxyls on tetrahedral Al (Al4C-�1-OH) while the bulk structure of α-Al2O3 is made of
octahedral Al. 1 Mo K-edge GI-EXAFS characterization of the model MoOx/α-Al2O3 system shows that
the adsorption mode of Mo oxoanions depends on the preparation method, the concentration of the
impregnation solution and the orientation of the Al2O3 surface revealing the different roles played by
the support. <strong>The</strong> (0001) surface is a simple physical container and precipitation of (NH4)2MoO4 is
observed. <strong>The</strong> (11 02) surface acts as a true supramolecular ligand with different oxoanions/support
interactions depending on the preparation method. As for impregnation, molecular recognition and
geometrical complementarity between the Al2O3 surface sites and the heptamolybdate (Mo precursor)
are observed leading to an oriented adsorption of Mo VI . As for equilibrium adsorption, molybdic
species are grafted through covalent bonds on Al4C-μ1-OH sites (Figure 1). Polarized Ni K-edge XAS
spectra were also recorded for supported model Ni catalysts and confirmed the specificity of each
Al2O3 orientations. XAS, in good agreement with ab-initio simulation spectra, shows an oriented
heterogeneous precipitation of α-Ni(OH)2 on the (11 02) orientation while no deposition of the Ni II
takes place on the (0001) surface.
<strong>The</strong> different reactivity toward adsorption of Mo on the model α-Al2O3 support can be related to the
surface OH on both faces: neutral non-reactive Al6C-μ2-OH on (0001) and acidic reactive Al4C-μ1-OH
on
morphology of �-Al2O3 particles (the catalytically relevant support) appears to be a key parameter for
a rational control of the active phase deposition.
(11 02). <strong>The</strong>se results shed light into the individual reactivity of Al2O3 surfaces and confirm that the
References.
1. A. Tougerti, C. Méthivier, S. Cristol, F. Tielens, M. Che and X. Carrier, Phys. Chem. Chem. Phys, 13 (2011) 6531-6543

What differs in the hydroxylation of supported MgO thin film
and MgO bulk surface ?
A combined STM/XPS answer
G. Cabailh 1 , R. Lazzari 1 , H. Cruguel 1 , J. Jupille 1 , L. Savio 2 , M. Smerieri 2,3 ,
A. Orzelli 3 , L. Vattuone 2,3 , M. Rocca 2,3
1
Institut des Nanosciences de Paris, CNRS and UPMC, 4 Place Jussieu, 75252 Paris, France
2
IMEM-CNR, Via Dodecaneso 33, 16146 Genova, Italy
3
Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy
<strong>The</strong> ubiquity of the interface between water and oxide materials has prompted a tremendous activity
to determine the adsorption mechanisms at the microscopic scale on crystalline surfaces of simple
oxides. On bulk MgO, the fivefold coordinated atoms of the basal (100) surface do not dissociate
isolated H2O molecules while H2O is easily dissociated at low-coordinated sites such as steps and
kinks. A puzzling case is the adsorption of H2O on metal-supported MgO films in the submonolayer
range of which coverage by OH groups has been estimated to 60 to 70% of a monolayer [1,2].
<strong>The</strong> extraordinary uptake of OH groups was attributed to the peculiarities of the electronic
properties of the thin supported MgO films [3]. However, density functional theory does not
support this view. Little changes in both the electronic structure and the capacity to dissociate H2O are
predicted for monolayer-thick MgO(100) islands that, at variance with experiment, are only expected
to dissociate H2O molecules along their borders [4].
Hydroxylation of submonolayers
of MgO(100)/Ag(100).
Left: XPS O 1s levels after
hydroxylation for substoichiometric
and close to stoichiometric
0.5 ML MgO films –
Right : 33×33 nm 2 STM image
of a MgO film after 2 L exposure
of water vapor.
In an attempt to solve the above discrepancies, MgO films of different stoichiometries were grown on
Ag(100) by reactive deposition of Mg in various O2 partial pressure [5]. <strong>The</strong> stoichiometry and,
consequently, the hydroxylation of the MgO films, was shown to strongly depend on the O2 pressure
during the film growth. Oxygen-deficient films undergo dramatic oxygen uptake by either exposure to
H2O or by aging in vacuum. Conversely, on stoichiometric MgO islands, x-ray photoemission
spectroscopy (XPS) analysis and scanning tunnelling microscopy (STM) images are consistent with
the prediction that H2O only dissociates at the island edges.
[1] S. Altieri et al., Phys. Rev. B. 76, 205413 (2007).
[2] L. Savio et al., J. Phys. Chem. B 108, 7771 (2004).
[3] S. Altieri et al., Thin Solid Films 400, 9 (2001).
[4] A. M. Ferrari et al., Phys. Chem. Chem. Phys. 9, 2350 (2007).
[5] G. Cabailh et al., J. Phys. Chem. A 115, 7161 (2011).

<strong>The</strong> Interaction of Water with High-index Anatase TiO2(105) Surface:
A First Principles Study
Qian Cuan and Xue-Qing Gong
State Key Lab of Chemical Engineering, Centre for Computational Chemistry and Research Institute
of Industrial Catalysis, East China University of Science and Technology, 130 Meilong Road,
Shanghai 200237, P.R. China
<strong>The</strong> interaction of water with metal oxide surfaces is of fundamental importance to various fields of
science, ranging from geophysics to catalysis and biochemistry. 1 Over the past several decades,
titanium dioxide (TiO2) has been extensively investigated both experimentally and theoretically, 2 due
to the pioneering work of Fujishima and Honda on the splitting of water on TiO2 electrodes. 3 Recently,
efficient scheme to synthesize anatase TiO2 with high index (105) facets have been devised, and this
well-faceted surface may have promising potential applications owing to the unique stepped atomic
configuration. 4 By means of density functional theory calculations and first-principles molecular
dynamics simulations of water adsorption properties at (105) surfaces with different possible
terminations, we demonstrate an atomic scale insights into understanding how the stoichiometric
(105) surface exhibits a preferred termination in water surrounding environment.
Figure: Calculated structures (side view) of three possible terminations of stoichiometric
anatase TiO2 (105) surface. O atoms are red, Ti atoms are light gray, and H atoms are white,
respectively.
We can clearly find that (105) facets are most possibly exposed by the first structure (Figure, left) in
vacuo, since it gives the best stability in surface energy calculation. At 1/4 ML water coverage,
dissociative adsorption is highly favoured at all three terminations, and it yields several adsorption
configurations. Along with the increasing coverage of the water adsorption in different combinations of
complexes, the augmentation of the corresponding adsorption energy is accompanied by significant
change of surface energy. This results in the change of relative stability of the terminations at full
water coverage and makes the third structure (Figure, right) which is the worst in vacuo to be the
most stable one.
(1) Henderson, M. A. Surf. Sci. Rep. 2002, 46, 5.
(2) Diebold, U. Surf. Sci. Rep. 2003, 48, 53.
(3) Fujishima, A.; Honda, K. Nature 1972, 238, 37.
(4) Jiang, H. B.; Cuan, Q. A.; Wen, C. Z.; Xing, J.; Wu, D.; Gong, X. Q.; Li, C. Z.; Yang, H. G. Angew.
Chem. Int. Edit. 2011, 50, 3764.

“Comparing surface oxides on AZ31 and AZ61 Magnesium alloys after a short time of
heat treatment at 200ºC”
Magnesium (Mg) is the lightest structural metal and its alloys provide numerous benefits as
engineering material where lightweight is an important requirement; however the industrial
deployment of Mg in most instances requires anti-corrosion coatings. Engineering the Mg surface is
an area that is recently undergoing intense research. Surface engineering commences with the
‘pretreatment step’ that can be used to modify the surface composition and morphology resulting in
surface enrichment or depletion of alloying elements.
In order to improve the surface properties of magnesium alloys AZ31 and AZ61 surface oxides were
characterized and compared on both alloys into two different surface states (As received and freshly
polished conditions) after being subjected to heat treatment at 200 ° C in air atmosphere for short
periods of time (5-60 min).
Due to the small thickness of the oxide layer formed, it is necessary to use high-resolution surface
analysis techniques to characterize them. <strong>The</strong>refore, the main technique of characterization has been
X-ray Photoelectron spectroscopy (XPS) accompanied by a system of ion sputtering. It has also been
performed thermal gravimetric analysis which has led to observe gains and/or mass loss obtained
during treatment.
Differences were observed in the mechanisms of growth of surface oxides on each surface
states/alloys and the growth of different species on the surface which could influence the protective
capabilities against corrosion of these layers.
Acknowledgment
"<strong>The</strong> authors gratefully acknowledge the financial support for this work from the Ministry of Science
and Innovation of Spain ( MAT 2009-13530)"

D. Z. Gao, M. B. Watkins, A. L. Shluger
Pd on MgO (001) : Transient Mobility Mechanisms
Adsorption of metal atoms and clusters on oxide surfaces and subsequent processes that occur play
an important role in surface coatings and film growth. When atoms/molecules adsorb on a surface,
energy is released and dissipated through various processes. <strong>The</strong>se processes can strongly influence
the final structure of thin film and island formation. Previous experimental results and rate calculations
suggested that deposited atoms may possess some mobility at temperatures where the contribution
from thermal diffusion processes should be negligible. <strong>The</strong>re is so far a lack of decisive evidence to
shed light on the mechanisms of the process itself. <strong>The</strong>re has been ample experimental data and
theoretical work on the topic both confirming and contradicting the existence of so called transient
mobility [1] of adsorbed species in various systems. Transient mobility of metal atoms on oxide
surfaces however has not been previously investigated.
<strong>The</strong> purpose of this study is to examine the adsorption of Pd atoms on the MgO (001) surface in order
to elucidate the mechanisms involved in transient mobility of metal atoms on oxide surfaces. Classical
molecular dynamics simulations were used to simulate Pd atoms colliding with an MgO (001) surface
terrace at incoming velocities and surface temperatures that correspond to common experimental
deposition conditions. Our calculations indeed show that for this system low temperature transient
mobility is expected. Analysis of the mechanisms of adsorption and subsequent diffusion processes
reveal a number of energy dissipation mechanisms. <strong>The</strong>se can be described as a combination of so
called ‘long jumps’ in surface hopping diffusion [2], scattering [3], stick-slip friction [4], and vibrational
relaxation into surface phonons. <strong>The</strong>se mechanisms help in understanding how quickly atoms
thermalize after first colliding with the surface and highlight factors that can affect the distance they
travel from the collision site. Our analysis demonstrates that in order for Pd atoms to transiently
diffuse for large distances, they must successfully transfer large amounts of incoming vertical velocity
to horizontal motion along the surface. <strong>The</strong> average diffusion distance from each collision site
depends mostly on the shape of the potential energy surface rather than the amount of energy gained
through the Pd-surface interaction. For example Pd atoms colliding with the surface above Mg sites
can undergo transient diffusion for more than 2 nm before becoming thermalized with the surface and
reaching the regime of thermally activated hoping. This distance is decreasing as the temperature is
increasing. On the other hand, Pd atoms colliding with the surface above O sites do not exhibit
transient mobility and dissipate their energy to surface phonons.
[1] W. F. Egelhoff and I. Jacob, Phys. Rev. Lett. 1989, 62, 921.
[2] T. T. Tsong, C. Chen, Nature 1992, 335, 328.
[3] J. R. Manson, Phys. Rev. B 1998, 58, 2253.
[4] L. Prandtl, Journal of Applied Mathematics and Mechanics 1928, 8, 85-106.

Oxygen adatoms on TiO2(110): Signature in photoelectron spectroscopy
Rob Lindsay 1 , J.P.W. Treacy 1 , F. Allegretti 2
1. Corrosion and Protection Centre, School of Materials, <strong>The</strong> University of Manchester, Sackville
Street, Manchester, M13 9PL, UK
2. Institute of Physics, Surface and Interface Physics, Karl-Franzens University Graz, A-8010,
Austria
TiO2(110)(1x1) has emerged as the substrate of choice for fundamental studies of metal oxide
surfaces. Given the perception that defects can dominate oxide surface chemistry, one focus of such
work has been the reactivity of the most common point defect on this surface, the bridge oxygen
vacancy (Ob-vac). For example, it is well established that this Ob-vac can dissociate H2O to form two
surface bridging hydroxyls (OHb). It can also cleave O2, resulting in self-annihilation along with
production of an oxygen adatom (Oad) that is bound to a surface titanium. Substantive evidence for
this second process is derived from both temperature programmed desorption measurements and
scanning tunnelling microscopy (STM) images. To date, however, Oad has proven spectroscopically
elusive, which is potentially a serious obstacle to full nanoscale understanding of its chemistry, as well
as other properties. Here, we present data illustrating that Oad can be detected by means of
photoelectron spectroscopy (PES), opening the way to further study.
Previously, both electron energy loss spectroscopy (EELS) and valence band PES have been applied
to TiO2(110)(1x1) surfaces expected to possess Oad’s . <strong>The</strong>re is no clear signature ascribable to Oad
in any of the presented data, although peaks associated with reduced Ti 3+ cations are diminished
indicating surface oxidation (the formal oxidation state of Ti in stoichiometric TiO2 is +4). Thus it has
been generally perceived that Oad on TiO2(110)(1x1) is not detectable by either EELS or valence band
PES. Here, we provide evidence that, at least for the latter technique, this presumption is invalid. To
achieve this goal, valence band and O 1s core level PES data have been recorded from
TiO2(110)(1x1) surfaces prepared to exhibit either Ob-vac’s, OHb’s, or Oad’s.

Adhesion forces at zinc/α-Al2O3(0001) interface
Rémi Cavallotti, Jacek Goniakowski, Rémi Lazzari, Jacques Jupille,
Institut des nano sciences de Paris, Université Pierre et Marie Curie, France
Alexey Koltsov, Didier Loison
Arcelor Mittal Research Maizières-les-Metz,France
Understanding microscopic mechanism determining the properties of metal/oxide interfaces is of a
key importance in various domains of applicative research, ranging from microelectronic, to corrosion
and catalysis. In the field of iron industry, new steels known as “high elastic limit” are enriched in
oxidable additional elements like aluminum. During annealing which precedes galvanization,some
alloy elements oxidize and form particles or films on steel surface, what may reduce or even prevent
adhesion of zinc coating. In order to identify factors behind the adhesion strength at such oxide/zinc
interfaces, and to help developing and optimizing efficient anticorrosive coatings, we have studied
model Zn/α-Al2O3(0001) interfaces using both surface science experimental techniques and ab
initionumerical modeling.
Experimentally, zinc deposition was followed by SDR to determine contact angle and aggregates’
geometry on alumina. Three monolayers were deposited on substrate by variation of oxygen partial
pressure (10-9mbar –10-6mbar) and the temperature (T°C ambient –450°C). <strong>The</strong> hotter substrate is
the better adhesion is. A great oxygen partial pressure increases affinity between zinc and alumina.
In parallel, with an ab initio approach based on DFT (LDA and GGA) we have studied the adhesion
properties at Zn/α-Al2O3(0001) interfaces. Three alumina (0001) surface terminations (single Al layer,
double Al layer and O termination) have been considered, under vacuum (bare) or in presence of
water vapor (fully hydrogenated). While in vacuum the most stable surface is terminated by a single Al
monolayer (non polar termination), hydrogenation strongly stabilizes the O-terminated surface (polar
termination). Zinc (both ad-atoms and constitute deposits) adsorb the best on bare polar terminations.
However, surface hydrogenation does efficiently block the metal-oxide interaction.

Title: Interfactant-mediated growth of rare-earth oxides on silicon
J. Ingo Flege•, B. Kaemena•, S. Gevers†, J. Höcker•, F. Bertram‡, J. Wollschläger†, and Jens Falta•
•Institute of Solid State Physics, University of Bremen, 28359 Bremen, Germany
†Department of Physics, University of Osnabrück, 49069 Osnabrück, Germany
‡Hamburger Synchrotronstrahlungslabor am Deutschen Elektronensynchrotron, 22607 Hamburg,
Germany
Title: Interfactant-mediated growth of rare-earth oxides on silicon
<strong>The</strong> growth of high-quality, epitaxial thin oxide films on silicon is a long-standing goal in
semiconductor technology. Among other multiple possible applications, rare-earth (RE) oxides are
some of the most promising candidates for the realization of "high-k" dielectrics due to their predicted
high thermodynamic stability and their almost vanishing lattice mismatch to silicon. However, growth
of high-quality ultrathin films has so far been considerably impeded by RE-promoted Si oxidation at
the interface, resulting in subsequent silicate and silicon oxide formation. In this contribution, we
present an extensive study of epitaxial ceria [1] and praseodymia [2] films grown on Cl-passivated
Si(111) by molecular beam epitaxy.
X-ray photoemission spectroscopy is employed to investigate the stoichiometry of the as-prepared
films, proving the sole existence of RE2O3 after the preparation as well as the formation of
continuous RE oxide films. Truly ultrathin films of a few monolayer (ML) thickness were characterized
by low-energy electron diffraction and X-ray standing waves (XSW) using Ce-Lα fluorescence and
Ce(Pr)-3d photoelectrons as secondary signal. In all circumstances, the XSW results unanimously
confirm the improved quality obtained by Cl preadsorption for both ceria and praseodymia (Fig. 1).
Furthermore, the atomic structure and chemical composition of the interface were inferred from
chemically-sensitive XSW measurements employing O1s photoelectrons, which allow to separately
investigate the atomic structure of the different oxygen species in the interface region. Moreover,
monitoring the Cl binding sites with XSW enabled us to draw conclusions on its role in the growth
process. Finally, for praseodymia and ceria film thicknesses exceeding a few nanometers, their
crystallinity, surface and interface roughness, and structure were characterized by X-ray reflectivity
and grazing-incidence X-ray diffraction.
Figure 1: XSW results for the growth of ultrathin cerium oxide (left) and praseodymium oxide
(right) films on Si(111) with and
without Cl preadsorption by molecular beam epitaxy.
[1] J.I. Flege, B. Kaemena, S. Gevers, F. Bertram, J. Höcker, T. Wilkens, D. Bruns, J. Bätjer, J.
Wollschläger,
J. Falta, submitted (2011).
[2] S. Gevers, J.I. Flege, B. Kaemena, D. Bruns, T. Weisemoeller, J. Falta, J. Wollschläger, Appl.
Phys. Lett.
97, 242901 (2010).

Poster Session 2
Hydrogenation of Unsaturated Hydrocarbons over Fe3O4 Supported Pd Nanoparticles:
Activation and Reactivity of the pro-chiral Molecule Isophorone
C.P. O’Brien, K.-H. Dostert, A. Savara, W. Ludwig, S. Schauermann and H.-J. Freund
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Recent progress in understanding the micro-kinetics and the reaction mechanism of the
hydrogenation of simple unsaturated compounds on oxide-supported Pd nanoparticles [1, 2] opened
up opportunities to investigate more complex systems. <strong>The</strong> aim of the long term project is to study the
mechanism and the kinetics of heterogeneous enantioselective hydrogenation over Palladium on a
prototypical compound.
Currently we focus on the selective hydrogenation of the pro-chiral molecule Isophorone, which
contains conjugated C=O and C=C bonds. In the first step we studied the adsorption properties of
Isophorone on Pd(111), Fe3O4, and Fe3O4-supported Pd nanoparticles by different techniques: IRAS
measurement and Temperature Programmed Desorption (TPD) in a UHV molecular beam setup was
combined with Synchrotron NEXAFS experiments. <strong>The</strong> experimental results reveal a partially
dehydrogenation of Isophorone on Pd at low temperature and a mostly flat adsorption geometry.
<strong>The</strong>se results get strongly supported by theoretical calculations [3].
Additionally, we present first results on the selective hydrogenation of Isophorone over Pd(111). We
show that predominant hydrogenation of the C=C entity occurs and nearly no hydrogenation of the
C=O functional group is detected.
1. Neyman, K.M. and S. Schauermann, Hydrogen Diffusion into Palladium Nanoparticles:
Pivotal Promotion by Carbon. Angewandte Chemie-<strong>International</strong> Edition, 2010. 49(28): p.
4743-4746.
2. Wilde, M., et al., Influence of Carbon Deposition on the Hydrogen Distribution in Pd
Nanoparticles and <strong>The</strong>ir Reactivity in Olefin Hydrogenation. Angewandte Chemie-
<strong>International</strong> Edition, 2008. 47(48): p. 9289-9293.
3. Liu, W., et al., Towards Low-temperature Dehydrogenation Catalysis: Isophorone on Pd(111).
in preparation.

Probing the Mechanism of Low Temperature CO Oxidation on Au/ZnO Catalysts by
Vibrational Spectroscopy
Heshmat Noei and Yuemin Wang
Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44801 Bochum, Germany
Recently, oxide-supported gold nanoparticles (NPs) have attracted enormous attention from both
fundamental and technological perspectives due to their unique catalytic properties for a number of
chemical reactions, in particular for CO oxidation at low temperatures. To date, numerous
experimental and theoretical studies have been reported on this system. It has been proposed that
the reactivity of Au nanoparticles is related to many factors such as the particle size and shape, the
Au-support charge transfer, the role of low-coordinated sites, the nature of the support as well as the
preparation methods. Despite extensive investigations, however, the origin of the catalytic activity of
gold NPs is still under debate and a detailed atomic-scale understanding of the mechanism of CO
oxidation on Au-based catalysts represents a major challenge.
In this paper, we report on a systematic study of low-temperature CO oxidation on clean and
differently pre-treated Au/ZnO catalysts by FTIR spectroscopy using a novel ultra-high vacuum (UHV)
system [1-4]. <strong>The</strong> high-quality FTIR data provide detailed insight into the catalytic mechanism of lowtemperature
CO oxidation on differently pretreated Au/ZnO catalysts. For the samples without O2
pretreatment, negatively charged Au nanoparticles are identified which exhibit high reactivity to CO
oxidation at 110 K yielding CO2 as well as carbonate species bound to various ZnO facets. <strong>The</strong> O2
pretreatment leads to the formation of metallic Au 0 nanoparticles, where CO is activated at the
interface between the Au nanoparticles and the ZnO support. <strong>The</strong>se CO species undergo oxidation at
110 K yielding CO2 and different carbonate species. <strong>The</strong> latter are preferentially formed via the
interaction of formed CO2 with surface oxygen atoms on ZnO. In addition, it was found that the
activation of molecular O2 takes place on the Au surface and is promoted by pre-adsorbed CO.
References
1. H. Noei, C. Wöll, M. Muhler, Y. Wang, Appl. Catal. A: General, 391 (2001) 31.
2. H. Noei, C. Wöll, M. Muhler, Y. Wang, J. Phys. Chem. C, 115 (2011) 908.
3. H. Noei, H. Qiu,Y. Wang, M. Muhler, C. Wöll, ChemPhysChem, 11 (2010) 3604.
4. H. Noei, H. Qiu, Y. Wang, E. Löffler, C. Wöll, and M. Muhler, Phys. Chem. Chem. Phys. 10
(2008) 7092.

Temperature and field dependent soft x-ray absorption (XAS) and magnetic circular dichroism
(MCD) study of self-doped 3d oxide nanostripes
F. Allegretti, 1, * S. Altieri, 2 W. Steurer, 1 M. Finazzi, 3 S. Surnev, 1 S. Valeri 2,4 and F.P. Netzer 1
1 Surface and Interface Physics, Institute of Physics, Karl-Franzens University Graz, A-8010 Graz,
Austria
*present address: Surface and Interface Physics, Physics Department E20, TU Munich, D-85748
Germany
2 Università di Modena e Reggio Emilia, via Campi 213/A, 41125 Modena, Italy
3 Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
4 CNR, Istituto Nanoscienze, Centro S3, via Campi 213/a, 41125 Modena, Italy
We present the first results of a temperature- and magnetic field-dependent XAS and MCD
investigation on recently discovered [1-4] self-doped 3d transition metal oxide nanostructures with
atomic structure of the type c(4×2)Mn3O4/Pd. Such structures bear promise of exciting properties
stemming from their compressive strain state, their low dimensionality and the presence of a rhombic
array of regularly distributed cation vacancies.
<strong>The</strong> main goals of the project are: i) verify recent theoretical predictions of a ferromagnetic ground
state in this intriguing system [3]; ii) search for strong magnetic anisotropy phenomena; iii)
spectroscopically establish cation valence and spin character as well as orbital and spin contribution
to the ground state magnetic moment, i.e. the basic elements determining electronic structure and
underlying magnetic properties of 3d magnetic oxides.
For paramagnetic 25 Å wide c(4×2) Mn3O4/Pd nanostripes, in particular, we have detected a clear
magnetic anisotropy in the temperature- and field-dependent Mn L2,3 MCD spectra, which we relate to
the presence of a largely unquenched orbital moment and to the onset of a substantial orbital
polarization, as revealed by MCD sum rules analysis. This suggests that strongly anisotropic
electrostatic coupling in paramagnetic oxide nanostructures may provide an internal source of spatial
symmetry breaking, thus disclosing yet unexplored frontiers of orbital physics with possible
implications extending in much wider fields of magneto-transport research.
Future development of this research involving engineered Pd-supported monoatomic chains of
MnO2 and CoO2 oxide nanostructures are discussed in view of the influence that the one-dimensional
character and the total absence of Mn-O-Mn and Co-O-Co 180 o chemical bonds may have on the
electronic and magnetic correlations in both the ground state and the excited states of these onedimensional
3d oxide nanowires.
(c) (d)
Work supported by the ERC Advanced Grant SEPON.
Fig.1 c(4×2) Mn3O4/Pd(1,1,21) nanostripes:
(a) STM and (b) LEED. (c) Low temperature
and high magnetic field XAS and MCD Mn L2,3
spectra. (d) Magnetization curves for
different sample orientations.

Self-Trapping of Holes at the Surface of Monoclinic Zirconium Dioxide
MATTHEW J. WOLF (1)
Keith P. McKenna (1,2,3)
Alexander L. Shluger (1,2)
(1) University College London, London, UK
(2) WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, Japan
(3) University of York, York, UK
ZrO2 is one of the most important oxides for current and future technological applications, including
catalysis [1], fuel cells [2] and microelectronics [3]. On the other hand, hole-trapping, either intrinsic or
due to impurities, can play an important role in determining the electronic and optical properties of
oxide materials [4], and at the surface may impact upon catalytic properties due to the formation of
reactive O - species [5].
We have performed plane-wave DFT calculations to study the possibility of self-trapping of holes in
the bulk and at the most stable (-111) surface [6] of the low-temperature monoclinic phase of
zirconium dioxide (m-ZrO2). We have used the “Cancellation of Non-Linearity” method [7] to correct
the well-known self-interaction-error of DFT in its LDA and GGA flavours, thereby obtaining a reliable
description of these localised electronic states.
Oxygen ions in m-ZrO2 may be either 3-coordinated (3-C) or 4-coordinated (4-C), forming two 2D
sublattives. Our calculations predict that hole polarons are stable on the 3-C oxygen sublattice, with a
small trapping energy of 0.13 eV, but metastable on the 4-C sublattice. Adiabatic diffusion barriers,
calculated via a linear interpolation scheme, indicate that they are highly mobile, and may therefore
reach the surface. <strong>The</strong> (-111) surface possesses five symmetrically-inequivalent oxygen ions, which
are either 3-C or 2-C. Our calculations show that holes are trapped at 3-C sites by around 0.3 eV, and
at 2-C sites by over 1 eV. Calculation of the relevant diffusion barriers indicate that hole transport
takes place via direct hops between 2-coordinated sites, with an activation energy of 0.6 eV,
suggesting that diffusion may take place at moderate temperatures.
We will also discuss ongoing work studying hole-trapping at low-coordinated sites, such as stepedges
and kinks.
[1] J. W. Schwank and M. Di Battista, MRS Bull. 24 (1999)
[2] S. J. Park S, J. M. Vohs and R. J. Gorte, Nature 404 (2000)
[3] J. Robertson, Rep. Prog. Phys. 69 (2006)
[4] A. M. Stoneham et al., Journal of Physics: Condensed Matter 19 (2007)
[5] M. Che and A. J. Tench, Advances in Catalysis 31 (1982)
[6] A. Christensen and E. A. Carter, Physical Review B 58 (1998)
[7] S. Lany and A. Zunger, Physical Review B 80 (2009)

Heats of adsorption and surface reaction for carbon monoxide and oxygen on Pd
nanoparticles as determined by UHV single crystal adsorption microcalorimetry
S. Adamovsky, M. Peter, J.M. Flores- Camacho, J.-H. Fischer-Wolfarth,
S. Schauermann, H.-J. Freund
Understanding the energetics of surface processes and establishing the correlation with the structural
properties is an essential issue in heterogeneous catalysis. To establish this, one can obtain the heat
release during chemisorption or reaction. This can be realized by a method of single crystal
adsorption calorimetry (SCAC) that relies on measuring the temperature rise on ultrathin (1-10 µm)
single crystals during these processes with a pyroelectric detector [1,2].
We apply a newly developed SCAC set up [2] to determine the adsorption heats of carbon monoxide
and oxygen on Pd nanoparticles, supported on a well-defined Fe3O4/Pt(111) film [3]. To address the
size dependent properties the adsorbate-particle system, the nanoparticle size was varied in the
range of ~ 100 to 5000 Pd atoms per cluster. We observe different trends for the particle size
dependence of the CO and O adsorption energies and provide the first direct experimental
observation that the CO adsorption energy decreases with decreasing particle size. This result is in
line with the theoretical studies [4]. By measuring the CO adsorption energies on the oxygen
precovered Pd nanoparticles and Pd(111) at different temperatures, the CO-O interaction energies
and the heats of the CO oxidation reaction on the surface were determined.
References
[1] Campbell C. T., et al., Rev. Sci. Instr. 2004, 75 11.
[2] Fischer-Wolfarth J.-H., et al., Rev. Sci. Instrum. 2011, 82 2.
[3] Fischer-Wolfarth J.-H., et al., Phys. Rev. B. 2010, 81, 241416-(R)
[4] Yudanov I. V., et al., J. Phys. Chem. C 2008, 112, 20269

Title:Controlling the structure of CeO2 nanoparticles grown on Cu2O thin films
Authors: Dario Stacchiola, Jan Hrbek, Ping Liu, Jose Rodriguez
To rationalize structure-reactivity relationships for mixed-metal oxide catalysts, well-defined systems
are required. Ceria nanostructures are grown on an oxidized Cu(111) substrate and characterized
using scanning tunneling microscopy (STM). <strong>The</strong> structure of the ceria nanoparticles can be tune by
modifying the Cu2O film substrate. Copper and cerium oxides are cost effective materials widely used
in catalytic applications.
<strong>The</strong>se two materials individually are not ideal catalysts for reactions such as CO oxidation or the
water-gas shift (WGS) reaction. Reactivity studies are shown indicating that when ceria nanoparticles
are supported on Cu2O films grown on Cu(111), this inverse model catalyst becomes very active for
CO oxidation and the WGS.

Title: Oxidation and reduction of ultrathin silver films on Ni(111)
A. Meyer•, J. Ingo Flege•, S. D. Senanayake†, B. Kaemena•, R. E. Rettew‡, F. M. Alamgir‡, and Jens
Falta• •Institute of Solid State Physics, University of Bremen, 28359 Bremen, Germany †Chemistry
Department, Brookhaven National Laboratory, Upton, New York 11973, USA ‡ School of Materials
Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30322, USA
<strong>The</strong> improvement of solid state surfaces for technical purposes as, e.g., catalytic processes has
become of great interest in the last decades. <strong>The</strong> functionality of the surface region depends strongly
on its electronic and geometrical properties. Due to the partially filled d-band in the valence region,
transition metals offer a particular electronic structure and are preferred candidates as active
components. <strong>The</strong> combination of these transition metals with other metals allows for the creation of
novel materials with tunable chemical and electronic properties by electronic and structural
modification of the surface properties. In this contribution, we present an in-situ study of the oxidation
of ultrathin silver films on Ni(111) at oxidation temperatures of 500 K and 600 K investigated by lowenergy
electron microscopy (LEEM). Additionally, time-resolved intensity-voltage (I(V)) curves shed
light on the local film structure on a nanometer scale during the oxidation process. <strong>The</strong> silver film has
been prepared with a Knudsen cell evaporator under ultra-high vacuum (UHV) conditions. Silver
grows in a layer-by-layer mode up to the second monolayer at a temperature of 750 K, while the
LEED pattern shows a √ √ reconstruction of silver on Ni(111) [1]. Since the number of silver layers
can reliably be determined from its I(V) fingerprints [1], changes in local film thickness could be
followed for a mixture of one and two Ag monolayers during gas exposure. <strong>The</strong> in-situ study reveals
that oxidation with molecular oxygen [2] leads to a partial decomposition of the silver film with
subsequent relocation of the silver atoms and sequential coalescence to thicker silver patches (Fig. 1)
and concurrent evolution of Ag-free NiO(111) regions [2, 3]. <strong>The</strong> underlying mechanisms during
oxidation and the effect of subsequent reduction with ethylene will be discussed.
Figure 1: LEEM images of a one monolayer Ag film (a) before and (b) after oxidation taken at
4.8 eV electron energy and 20μm field of view. I(V) curves in (c), which have been collected at
the marked points in (a) and (b), show a distinct change in electron reflectivity after oxidation.
[1] A. Meyer, J. I. Flege, R. E. Rettew. S. D. Senanayake, Th. Schmidt, F. M. Alamgir, and J. Falta,
Phys. Rev. B 82, p. 085424 (2010) [2] A. Meyer, J. I. Flege, S. D. Senanayake, R. E. Rettew, F. M.
Alamgir, and J. Falta, IBM J. Res. Dev. 55, no. 4, p. 8 (2011) [3] J. I. Flege, A. Meyer, J. Falta, and E.
E. Krasovskii, Phys. Rev. B 84, p. 115441 (2011)

STRUCTURAL PROPERTIES AND PHOTOACTIVITY OF MIXED OXIDES ZrO2-TiO2
C. Gionco 1 , M. C. Paganini 1 , and E. Giamello 1
1 Università degli studi di Torino, Dipartimento di chimica IFM, Via P. Giuria 7, 10125, Italy, NIS Centre
of Excellence
Zirconium dioxide attracted great interest in the last decades because of the large range of
applications in the ceramic compounds fields, optical devices, gas sensors, catalysis (both as
catalysts and catalysts support) [1]. Our group deeply studied the mixed system ZrO2-TiO2 made to
improve thermal stability of ZrO2 [2]. In that study the system was calcined at a temperature of 500°C
and the result was a solid solution, mixture of tetragonal and monoclinic polymorphs of ZrO2. To
investigate the role of the phase and the defects coordination detected by means of EPR
spectroscopy some samples (ZrO2, ZrO2-TiO2 with 0.1, 1, 5, 10, 15% molar content of Ti) have been
calcined at a temperature of 1000°C in order to obtain samples containing a single polymorph. From a
structural (by means of XRPD and � -Raman spectroscopy) and spectroscopic (by means of Uv-Vis
DRS and EPR spectroscopy) systematic characterization important information about the role of the
crystallographic structure in the behaviour of those catalysts have been found.
[1] T. Yamaguchi Catal. Today 20 (1994) 199
[2] S. Livraghi et al. J. Phys. Chem. C 114 (2010) 18553

<strong>The</strong> Interaction of Biomolecules with Model Surfaces: Cystiene and RGD on TiO2 (110)
Joshua Muir a , Dominique Costa b , Hicham Idriss* c
a
Department of Chemistry, <strong>The</strong> University of Aberdeen, Aberdeen, UK.
b
Laboratoire de Physico-Chimie des Surfaces, UMR 7045, 75005 Paris, France.
c
SABIC T&I Riyadh, Riyadh, Saudi Arabia.
Ti and Ti alloys are important biomaterials used for implants and joints as they are non-toxic,
corrosion resistant and have high mechanical strength. <strong>The</strong> interaction of Ti implants with biological
material is therefore important in understanding how implants will behave in their target environment.
Ti in real environments, however, is covered in a poorly-defined oxide film which we shall represent
by modelling TiO2 surfaces rather than Ti.
Using plane-wave DFT we have modelled the interaction of a tripeptide (Arginine-Glycine-Aspartic
Acid RGD) with a representative Ti implant surface (rutile TiO2 (110)). RGD was chosen as
representative of the recognition sequence of intergrin binding to extracellular matrix proteins. RGD
adsorption has been compared to that of formic acid and single amino acids to examine the veracity
of these model compounds against a more accurate model.
Some examinations of RGD on TiO2 (110) surfaces (1-4) have been performed with classical force
fields calculations and water backgrounds. <strong>The</strong>se present disagreements upon the preferred binding
sites of RGD as well as presenting unusual binding geometries. By moving from a force field to a
planewave approach the proposed models can be tested at a higher accuracy.
Our results show that RGD on TiO2 adsorbs predominately through the carboxyl groups in dissociated
bridging fashion. <strong>The</strong> electronic nature of the RGD adsorption was found to be similar to that of
formate on the surface- a predominately Lewis Acid-Lewis Base type interaction between the electron
rich carboxylate O and the electron poor Ti atoms. In agreement with other amino acid studies on
metal oxides zwitterions were found to be less stable than neutral molecules (5, 6). <strong>The</strong> RGD
backbone had little effect on the adsorption geometry when compared to amino acid analogues but
had a large effect on the adsorption energy.
(1) Chen, M.; Wu, C.; Song, D.; Li, K., PCCP 2009, 12, 406.
(2) Wu, C.; Chen, M.; Guo, C.; Zhao, X.; Yuan, C., J. Phys. Chem. B 2010, 114, 4692.
(3) Song, D.; Chen, M.; Liang, Y.; Bai, Q.; Chen, J.; Zheng, X., Acta Biomater. 2010, 6, 684.
(4) Chen, M.; Wu, C.; Song, D.; Dong, W.; Li, K., J. Mater. Sci. Mater. Med. 2009, 20, 1831-1838.
(5) Gao, Y.K., Traeger, F., Shekhah, O., Idriss, H., Wöll, C., J. Colloid & Interface Science 2009,
338, 16–21.
(6) Wilson, J.N., Dowler, R.M., Idriss, H., Surf. Sci. 2011, 605, 206-213.

IWOX VIII Conference Attendees
Jie Zhang, East China University of Science and Technology
Qian Cuan, East China University of Science and Technology
Gilberto Teobaldi, University of Liverpool
Xueqing Gong, East China University of Science and Technology
Ulrike Diebold, TU Vienna
Scott Chambers, Pacific Northwest National Laboratory
Mario Chiesa, Universita di Torino
Ralf Bechstein, Aarhus University
Stefan Wendt, Aarhus University
Dario Stacchiola, Brookhaven National Laboratory
Xavier Carrier, Universite Pierre et Marie Curie
Geoffrey Thornton, University College London
Nicholas Harrison, STFC Daresbury Laboratory
David Grinter, University College London
Marco Nicotra, University College London
Lazzari Remi, INSP
Cavallotti Remi, INSP
Jupille Jacques, INSP
Goniakowski Jacek, INSP
Noguera Claudine, INSP
Bobby-Jean Shaw, University College London
Francesc Illas, Universitat de Barcelona
Gianfranco Pacchioni, Universita Milano Bicocca
Harald Brune, EPFL
Akira Otomo, Tokyo Institute of Technology
Hiroshi Onishi, Kobe University
Hajo Freund, Fritz Haber Institute of the Max Planck Society
Robert Lindsay, Manchester University
Serguei Adamovski, Fritz Haber Institute of the Max Planck Society
Axel Meyer, University of Bremen
Jan Ingo Flege, University of Bremen
Renald Schaub, University of St Andrews
Umberto Martinez Possoni, Aarhus University
Svetlozar Surnev, Karl-Franzens University Graz
Xiang Shao, Fritz Haber Institute
Miquel Salmeron, Lawrence Berkeley National Laboratory
Zednek Dohnalek, Pacific Northwest National Laboratory
Casey O’Brien, Fritz Haber Institute
Alejandro Samaniego,CENIM-CSIC
David Gao, University College London
Bruno Domenichini, Universite de Bourgogne
Paola Luches, CNR – Istituto Nanoscienze
Lorenzo Mino, University of Turin
Matthew Wolf, University College London
Salvatore Altieri, University of Modena
Helmut Kuhlenbeck, Fritz Haber Institute
Teng-Yan Chang, <strong>The</strong> University of Tokyo
Matthew Watkins, University College London
Frederico Sanches, Imperial College London
Monica Patel, Imperial College London
Ehsan Ahmad, Imperial College London
Chiara Gionco, University of Turin
Yuemin Wang, Ruhr University Bochum
Heshmat Noei, Ruhr University Bochum
Javier Fedz.Sanz, University of Seville
Hicham Idriss, SABIC and University of Aberdeen
Christof Wöll, Karlsruhe Institute of Technology
Sergio Tosoni, Universitat de Barcelona