Nanoparticle Interfaces Studied Using Environmental TEM ... · Liu, P., Madsen, J., Schiøtz, J.,...
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Nanoparticle Interfaces Studied Using Environmental TEM and Atomic Scale Modelling
Liu, Pei; Madsen, Jacob; Schiøtz, Jakob; Wagner, Jakob Birkedal; Hansen, Thomas Willum
Publication date:2016
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Citation (APA):Liu, P., Madsen, J., Schiøtz, J., Wagner, J. B., & Hansen, T. W. (2016). Nanoparticle Interfaces Studied UsingEnvironmental TEM and Atomic Scale Modelling. Poster session presented at 16th International Congress onCatalysis, Beijing, China.
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Nanoparticle Interfaces Studied Using
Environmental TEM and Atomic Scale Modelling Pei Liu*1, Jacob Madsen2, Jakob Schiøtz2, Jakob B. Wagner1 and Thomas W. Hansen1.1 Center for Electron Nanoscopy, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark2 Department of Physics, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark
Supported heterogeneous catalysts play an essential role in areas such as automotive exhaust abatement, energy storage/conversion and
sustainable production of chemicals. In order to gain insight into properties such as activity and stability of these materials, catalysts must be studied
in situ in reactive environments. Only a few experimental techniques allow for investigation of the materials at a local scale with atomic resolution
while exposing samples to gases and elevated temperatures. Recent advances in high-resolution environmental transmission electron microscopy
(ETEM) have shown that the atomic configuration at surfaces and interfaces of a metal nanoparticle is a function of its surroundings [1]. Similarly, the
dynamics and hence stability of the catalyst are important parameters which can be studied using in situ microscopy [2].
Motivation and background
AcknowledgementsWe kindly acknowledge the support of the The Danish Council for Independent Research | Technology and Production Sciences (FTP).
Furthermore, the A. P. Møller and Chastine Mc-Kinney Møller Foundation is gratefully acknowledged for their contribution to the
establishment of the Center for Electron Nanoscopy in the Technical University of Denmark.
email: [email protected]
References[1] H. Yoshida, Y. Kuwauchi, J.R. Jinschek, K. Sun, S. Tanaka, M. Kohyama, S. Shimada, M. Haruta, S. Takeda, Science
335, 317-319 (2012).
[2] T.W. Hansen, A.T. DeLaRiva, S.R. Challa, A.K. Datye, Accounts of Chemical Research 46, 1720-1730 (2013).
In order to study the influence of the environment on catalytic nanoparticles, model systems
consisting of Au/CeO2, Pt/CeO2, Au/TiO2, and Pt/TiO2 were prepared using a physical method
(sputter coating). For the preliminary in situ experiments low gas pressures at room temperature
were used.
ETEM experiments
1) Sputter coat prepared
Au/TiO2, exposed to
0.45 mbar CO dose rate:
4.27E+4 e-/Ųs.
2) FFT of Au particle and
TiO2 respectively,
Au(-1-11)||TiO2 (1-10).
3) Snap shots from an
image sequence, arrows
indicate the three top most
layers of the particle.
4) The number of atomic
columns in each layer of
the particle as seen in
image 3), the trend
indicates that the dynamics
is a fluctuating
phenomenon.
1)
3)
2)
4)
2)
Surface atom diffusion
Particle wiggling
1) Angle between Au(11-1) and CeO2(200) vesus time. 2) FFT of Au particle and TiO2 respectively,
Au(11-1)||CeO2(200); 3) two snap shots from an image sequence of Au/CeO2 (sputter coating
prepared) exposed to 0.017 mbar O2, dose rate: 4.54E+4 e-/Ųs .
34s 104s
1)
2)
3)
Supported nanoparticles are dynamic displaying both atomic scale diffusion and collective motion
of the entire particle. We can observe both of these phenomenons in situ with ETEM.
Precise information of what happens at the support interface is
not directly available from experiment. We are developing
theoretical models specifically for metal/oxide interfaces
relevant for catalytic systems. Three qualitatively different
examples are shown below.
Modelling support interfaces
4.3 %
- 4.3 %
Str
ain
Comparison between a free Pt nanoparticle and a similar
particle supported on anatase TiO2. The small lattice mismatch
of 3.4 % modifies the overall strain distribution.
7 %- 7 %
Strain
Pt nanoparticle supported on cubic ZrO2. The particle is unable
to adapt to the large lattice mismatch of 24 %, leading to a
disorganized strain distribution.
Cu nanoparticle supported on alumina. The strain distribution of
the bottom atomic layer of the particle reveals a dislocation
network at the interface.
Coherent interface
Semi coherent interface
Incoherent interface