Synthesis and quantum-chemical study of vanadium oxide structures on the silica surface and their interactions with pairs of VOCl3 and H2O

Author
A. I. Kutchiev
Year
2007
Language of the thesis
Russian
Thesis name in original language
Синтез и квантово-химическое исследование ванадий оксидных структур на поверхности кремнезема и их взаимодействия с парами VOCI3 и Н20
Abstract & Cover

1. For the first time, a comprehensive experimental and quantum-chemical study of vanadium-oxygen structures chemically bonded to the Si02 surface by a different number of Si-0-V bonds was carried out, which made it possible to describe the spectral, energy, and adsorption characteristics depending on their stoichiometry and local structure.

2. It is shown that for vanadium-containing clusters built on the basis of the minimal model of the silanol group - USi-OH - the spectral, structural and energy characteristics are predicted at a semi-quantitative level.

3. Quantum-chemical analysis showed that the energy effect of the addition of vanadium-oxygen groups depends on their functionality, and in the absence of steric hindrances, the formation of polyfunctional groups is energetically more favorable.

4. The possibility of spectral identification of vanadium-oxygen structures of different functionality has been experimentally shown and quantum-chemically substantiated: in the region of 920-940 cm"1, one should expect the manifestation of Si-OV stretching vibrations of vanadium-oxygen structures that form two and three bonds with eighteen the surface of the substrate, and in the range of 950-970 cm "1 - monodentant groups with a single Si-0-V bond.

5. On the basis of diffuse reflectance electron spectroscopy, adsorption studies and quantum chemical modeling, it has been shown that the interaction of vanadium-oxygen groups with water vapor can lead to competing processes: adsorption interaction and hydrolytic destruction of Si-0-V bonds.

6. Quantum-chemical analysis has shown that the energy effect is successively reduced by the adsorption of water by a hydrogen bond, adsorption by the coordination mechanism, and hydrolytic destruction of Si-0-V bonds, and the latter process may be of an activation nature. At the same time, monodentate vanadium-oxygen groups are characterized by the greatest energy effect during adsorption, but at the same time they are the least resistant to degradation under the action of water.

7. For the first time, a quantum-chemical analysis of possible chemical transformations as a result of two MN cycles has been carried out. In the second MN cycle, it is energetically more favorable to form bidentate vanadium-oxygen groups chemically bonded to structures that form one Si-0-V bond with the silica surface.

Source of Information
Malygin et al., Chem. Vap. Deposition 21 (2015) 216-240
University
Saint-Petersburg State Technological Institute (SPbSTI)
(Saint Petersburg, Russia)
Other notes
Note Riikka 14.6.2019. Title originally in this file was: "Synthesis and quantum-chemical study vandieken structures on the silica surface and their interaction with pairs of VOCl3 and H2O". Has been retranslated in VPHA (Puurunen, Yurkevich)
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