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Z-contrast imaging of supported Pt and Pd clusters
S A Bradley1, M J Cohn, S J Pennycook
1UOP Research Center, Des Plaines, Illinois 60017.
Microscopy Research and Technique
|August 1, 1994
Summary
High-angle annular dark-field microscopy revealed that supported metal catalysts are composed of nanometer-sized clusters. Different metals resulted in varying cluster sizes, with palladium clusters showing distinct grouping.
Area of Science:
- Materials Science
- Nanotechnology
- Catalysis
Background:
- Supported metal catalysts are crucial in various chemical processes.
- Understanding the nanoscale structure of these catalysts is essential for optimizing their performance.
- Previous characterization methods had limitations in resolving individual nanoclusters.
Purpose of the Study:
- To investigate the size and dispersion of metal nanoclusters on catalyst supports.
- To determine if different metals exhibit distinct cluster characteristics.
- To confirm the aggregation behavior of specific metal clusters, such as palladium.
Main Methods:
- High-angle annular dark-field (HAADF) microscopy, also known as Z-contrast imaging.
- Analytical electron microscopy (AEM).
Main Results:
- HAADF microscopy confirmed that well-dispersed metal supported catalysts consist of nanometer-sized clusters.
- The size of these metal clusters varied depending on the specific impregnated metal.
- Analytical electron microscopy provided evidence for the grouping and aggregation of palladium (Pd) clusters.
Conclusions:
- Supported metal catalysts are indeed composed of distinct nanometer-sized clusters.
- Metal type is a key factor influencing the size of these catalytic nanoclusters.
- Palladium clusters exhibit a tendency to group together on catalyst supports.