 |
INTERPRETATION
OF HREM IMAGES OF SUPPORTED CATALYSTS |
|
|
INTERPRETATION
OF HREM IMAGES OF SUPPORTED CATALYSTS |
|
The interpretation of contrasts of HREM images recorded on supported catalysts can only be attained with the use of Image Simulation Techniques. Complex structural models are usually required to perform this task. Our group has developed a specific program, RHODIUS, which allows to build supercells in which the features of nanosized supported phases can be modelled very flexibly and with a precise control [1-2]. Among other features RHODIUS allows one to define size and shape of the supported nano-crystal, orientation relationship with the support, exact position of the supported crystal on the support surface, details of the surface structure of both supported and support phases or details of the interface structure.
Supercells like those shown in the examples below can be used as input to any simulation program. In our case we have used the models to simulate Electron Microscopy data, such as HREM images or Electron Diffraction Patterns. Other applications are possible in any case.
Click here if you want to
install Rhodius program
If you can not see properly the models on the right, you need
to install Chime plug-in from MDL.
| Cuboctahedral rhodium particle with hexagonal (111) and square (100) faces (405 atoms). | |
55-atom cuboctahedron model for Pt particles in Pt/SiO2 catalysts (EuroPt-1). Exposed faces are triangular (111) and square (100). |
|
Rh supported on CeO2 |
Use the mouse to play with the structural models:
| Case 1: Pt/Ce0.8Tb0.2Ox reduced at 700ºC in H2/Ar | ||
Experimental HREM Image |
Structural Model |
Image simulated from the model |
|
|
|
| Case 2: Nd2O3/MgO catalyst | ||
Experimental HREM Image |
Structural Model |
Image simulated from the model |
|
|
|
| Case 3: Pt/Ce0.8Tb0.2Ox reduced at 900ºC in H2 | ||
Experimental HREM Image |
Structural Model |
Image simulated from the model |
|
|
|
| Case 4: Rh/CeO2 reduced at 900ºC in H2 | ||
Experimental HREM Images |
Structural Model |
Images simulated from the model |
|
|
|
 |
 |
|
[1] S. Bernal, F.J. Botana,
J.J. Calvino, C. López Cartes, J.A. Pérez Omil y J.M. Rodríguez-Izquierdo, “ THE
INTERPRETATION OF HREM IMAGES OF SUPPORTED METAL CATALYSTS USING IMAGE SIMULATION: PROFILE
VIEW IMAGES”.
Ultramicroscopy, 72 (1998)
135-164
[2] C.
López-Cartes, J.A. Pérez-Omil, J.M. Pintado, J.J. Calvino, Z.C. Kang, L.
Eyring, “RARE-EARTH OXIDES WITH FLUORITE-RELATED STRUCTURES: THEIR SYSTEMATIC
INVESTIGATION USING HREM IMAGES, IMAGE SIMULATION AND ELECTRON DIFFRACTION PATTERN
SIMULATIONS”.
Ultramicroscopy, 80 (1999)
19-39
