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In-Situ HREM Observation of Reduction of PdO to Pd Metal

Published online by Cambridge University Press:  02 July 2020

Peter A. Crozier
Affiliation:
Center for Solid State Science, Arizona State University, Tempe, AZ85287-1704
Abhaya K. Datye
Affiliation:
Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM87131
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Extract

A detailed understanding of phase transformation mechanisms in small particles is critical for the design of small metal particle catalysts and nanophase materials. For palladium supported on silica, it is known that under certain conditions, reduction of PdO can lead to the formation of small Pd metal particles containing central faceted voids[l]. In-situ microscopy studies show that the voids form when PdO is reduced at temperatures between 200 and 400°C but collapse when the temperature reaches about 550°C [2]. Here we present in-situ high resolution microscopy showing the details of the void formation process.

Model Pd/SiO2, catalysts were prepared by dispersing Pd metal over silica microspheres using techniques described elsewheretl]. The Pd/SiO2, catalyst were fully oxidize°C for 2 hours. The catalyst was crushed and dispersed over Mo grids and plasma cleaned to remove any residual carbonaceous material. A Philips CM 200 with a slow scan CCD camera and video recording system was used to recording HREM images during in situ reduction at 200°C.

Type
In-Situ Microscopy Techniques
Copyright
Copyright © Microscopy Society of America

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References

REFERENCES

1.Datye, AK, Kalakkad, DS, Völkl, E, Allard, LF (1995). Electron Holography of Heterogeneous Catalysts. Electron Holography (Elsevier Science, Amsterdam), 199208.Google Scholar
2.Crozier, PAet al (1998). Microscopy and Microanalysis 4, 278285.CrossRefGoogle Scholar