Cation induced changes in chemical reactivity of small metal particles

R. A. Van Santen; A. P.J. Jansen

Cation induced changes in chemical reactivity of small metal particles

R. A. Van Santen, A. P.J. Jansen

Inorganic Materials & Catalysis

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

The chemical reactivity of small metal clusters dispersed in microcavities of zeolites is shown to be significant by the function of local cation environment. Adsorption properties of CO or Lewis bases are also found to be changed. Here we report HFS-LCAO calculations of CO, H₂ and H-atoms chemisorbed to small Ir₄ clusters in the presence of a Mg²⁺-ion. Analysis of our results shows that the chemical reactivity of CO, and also its infrared spectra, should be a sensitive function of the relative positions of adsorbate, Ir₄ cluster and cation. This appears also the be the case for H₂ chemisorption. But the effects are different. Whereas the Co bond appears to be strengthened when the Ir₄ cluster is in between the Mg²⁺-ions and CO, the reverse is found for H₂. the bondstrength of chemisorbed H₂ appears to be significantly weakened due to the presence of the Mg²⁺-ion. It appears to be mainly due to the reduced repulsive interactions between H₂ and Ir₄. The result of these calculations will be analyzed with respect to their catalytic implications.

Original language	English
Number of pages	1
Journal	Preprints - American Chemical Society, Division of Petroleum Chemistry
Volume	35
Issue number	1
Publication status	Published - 1 Dec 1990

Cite this

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title = "Cation induced changes in chemical reactivity of small metal particles",

abstract = "The chemical reactivity of small metal clusters dispersed in microcavities of zeolites is shown to be significant by the function of local cation environment. Adsorption properties of CO or Lewis bases are also found to be changed. Here we report HFS-LCAO calculations of CO, H2 and H-atoms chemisorbed to small Ir4 clusters in the presence of a Mg2+-ion. Analysis of our results shows that the chemical reactivity of CO, and also its infrared spectra, should be a sensitive function of the relative positions of adsorbate, Ir4 cluster and cation. This appears also the be the case for H2 chemisorption. But the effects are different. Whereas the Co bond appears to be strengthened when the Ir4 cluster is in between the Mg2+-ions and CO, the reverse is found for H2. the bondstrength of chemisorbed H2 appears to be significantly weakened due to the presence of the Mg2+-ion. It appears to be mainly due to the reduced repulsive interactions between H2 and Ir4. The result of these calculations will be analyzed with respect to their catalytic implications.",

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T1 - Cation induced changes in chemical reactivity of small metal particles

AU - Van Santen, R. A.

AU - Jansen, A. P.J.

PY - 1990/12/1

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N2 - The chemical reactivity of small metal clusters dispersed in microcavities of zeolites is shown to be significant by the function of local cation environment. Adsorption properties of CO or Lewis bases are also found to be changed. Here we report HFS-LCAO calculations of CO, H2 and H-atoms chemisorbed to small Ir4 clusters in the presence of a Mg2+-ion. Analysis of our results shows that the chemical reactivity of CO, and also its infrared spectra, should be a sensitive function of the relative positions of adsorbate, Ir4 cluster and cation. This appears also the be the case for H2 chemisorption. But the effects are different. Whereas the Co bond appears to be strengthened when the Ir4 cluster is in between the Mg2+-ions and CO, the reverse is found for H2. the bondstrength of chemisorbed H2 appears to be significantly weakened due to the presence of the Mg2+-ion. It appears to be mainly due to the reduced repulsive interactions between H2 and Ir4. The result of these calculations will be analyzed with respect to their catalytic implications.

AB - The chemical reactivity of small metal clusters dispersed in microcavities of zeolites is shown to be significant by the function of local cation environment. Adsorption properties of CO or Lewis bases are also found to be changed. Here we report HFS-LCAO calculations of CO, H2 and H-atoms chemisorbed to small Ir4 clusters in the presence of a Mg2+-ion. Analysis of our results shows that the chemical reactivity of CO, and also its infrared spectra, should be a sensitive function of the relative positions of adsorbate, Ir4 cluster and cation. This appears also the be the case for H2 chemisorption. But the effects are different. Whereas the Co bond appears to be strengthened when the Ir4 cluster is in between the Mg2+-ions and CO, the reverse is found for H2. the bondstrength of chemisorbed H2 appears to be significantly weakened due to the presence of the Mg2+-ion. It appears to be mainly due to the reduced repulsive interactions between H2 and Ir4. The result of these calculations will be analyzed with respect to their catalytic implications.

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Cation induced changes in chemical reactivity of small metal particles

Abstract

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