Xanes and 51V Nmr study of vanadium-oxygen compounds

Nabavi, Majid; Taulèlle, Francis; Sánchez, Clément; Verdaguer, Michel

doi:10.1016/0022-3697(90)90020-g

Cited by 55 publications

(54 citation statements)

References 23 publications

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“…The V K-edge XANES spectra should also be sensitive to the coordination environment of the vanadium atom; the spectra are shown in Figure 6. Square-pyramidal VO 5 units containing a V=O bond have been reported [26] to exhibit a pre-edge feature at 5468.6 to 5469.5 eV, and in our spectra this feature is observed at 5469 eV. In VO 4 units this feature was at lower energy, 5467.8 eV, though it was shifted to higher energy (5468.3 eV) if one of the bonds was a V=O.…”

Section: Structure Investigation By X-ray Absorption Spectroscopysupporting

confidence: 55%

“…In VO 4 units this feature was at lower energy, 5467.8 eV, though it was shifted to higher energy (5468.3 eV) if one of the bonds was a V=O. [26] Hence the position of this feature is more sensitive to the presence of a V=O double bond than to the coordination number, and the presence of a double bond is confirmed by IR and Raman spectroscopic evidence. The intensity of this feature is found to be sensitive to the coordination number: with VO 5 it was 0.51-0.74 times the edge jump, whereas with VO 4 it was 0.82-1.09 times the edge jump; with VO 4 containing a V=O this coefficient was 0.96.…”

Section: Structure Investigation By X-ray Absorption Spectroscopymentioning

confidence: 79%

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Synthesis, Spectroscopic and Structural Studies on Vanadium(V) Periodates

Hector

Levason

2011

Eur J Inorg Chem

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Keywords: Vanadium / Periodate / EXAFS spectroscopyReactions of V 2 O 5 or NH 4 VO 3 with periodic acid under basic conditions followed by acidification result in precipitates of general formula M 5 V 4 I 2 O 19 (OH)·nH 2 O (M = Na, n = 10; M = K, n = 5; M = Rb, n = 4; M = Cs, n = 3; M = NH 4 , n = 11). These are amorphous, and attempts at crystallisation failed, but spectroscopic measurements and analysis show similar

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Section: Structure Investigation By X-ray Absorption Spectroscopysupporting

confidence: 55%

Section: Structure Investigation By X-ray Absorption Spectroscopymentioning

confidence: 79%

Synthesis, Spectroscopic and Structural Studies on Vanadium(V) Periodates

Hector

Levason

2011

Eur J Inorg Chem

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“…The Fe2p regions for the three VFe 2 O x aerogels consist of broad peaks that generally do not differ between the various heat treatments. [42][43][44] The pre-edge peak intensity also increases with greater VO 6 octahedral distortion and to a lesser degree with increasing density of unoccupied d states that accompany higher V oxidation states. 40 The O1s spectra of all three samples are similar, and indicative of hydrated or defective oxides.…”

Section: Characterization Of Vfe 2 O X Aerogel Structure and Compositionmentioning

confidence: 99%

Defective by design: vanadium-substituted iron oxide nanoarchitectures as cation-insertion hosts for electrochemical charge storage

Chervin

Miller

et al. 2015

J. Mater. Chem. A

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Vanadium-substituted iron oxide aerogels (2 : 1 Fe : V ratio; VFe 2 O x ) are synthesized using an epoxideinitiated sol-gel method to form high surface-area, mesoporous materials in which the degree of crystallinity and concentration of defects are tuned via thermal treatments under controlled atmospheres. Thermal processing of the X-ray amorphous, as-synthesized VFe 2 O x aerogels at 300 C under O 2 -rich conditions removes residual organic byproducts while maintaining a highly defective g-Fe 2 O 3 -like local structure with minimal long-range order and vanadium in the +5 state. When assynthesized VFe 2 O x aerogels are heated under low partial pressure of O 2 (e.g., flowing argon), a fraction of vanadium sites are reduced to the +4 state, driving crystallization to a Fe 3 O 4 -like cubic phase.Subsequent thermal oxidation of this nanocrystalline VFe 2 O x aerogel re-oxidizes vanadium +4 to +5, creating additional cation vacancies and re-introducing disordered oxide domains. We correlate the electrochemical charge-storage properties of this series of VFe 2 O x aerogels with their degree of order and chemical state, as verified by X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. We find that the disordered O 2 -heated VFe 2 O x aerogel yields the highest Li +and Na + -insertion capacities among this series, approaching 130 mA h g À1 and 70 mA h g À1 , respectively. Direct heat-treatment of the VFe 2 O x aerogel in flowing argon to yield the partially reduced, nanocrystalline form results in significantly lower Li + -insertion capacity (77 mA h g À1 ), which improves to 105 mA h g À1 by thermal oxidation to create additional vacancies and structural disorder.

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“…During this process, the ammoniumpropyl chains used for functionalization are removed from the pores. [22] and Mg 3 V 2 O 8 [23,24]. Also, the corresponding Raman spectra are dominated by a band at 1040 cm )1 (see inset), which has been assigned to isolated tetrahedral VO 4 with three V-O support bonds and one V@O bond in the literature [25][26][27][28][29].…”

Section: Synthesis Of Vo X /Sba-15mentioning

confidence: 99%

Partial Oxidation of Methanol Over Highly Dispersed Vanadia Supported on Silica SBA-15

et al. 2005

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The partial oxidation of methanol to formaldehyde (FA) was studied over highly dispersed vanadia supported on mesoporous silica SBA-15 (VO x /SBA-15). VO x /SBA-15 catalysts were prepared by a novel grafting/ion-exchange method and characterized using UV-VIS-and Raman spectroscopy. The resulting surface vanadium oxide species (0-2.3 V/nm 2 ), grafted on the inner pores of the SBA-15 silica matrix, consist of tetrahedrally coordinated monomeric and polymeric vanadia. The VO x /SBA-15 catalysts are active and highly selective for the production of FA between 300 and 400°C. Comparison of the reactivity results with literature data reveals that a better catalytic performance can be obtained over vanadia supported on mesoporous silica in comparison with conventional silica samples with the same vanadium loading. Raman characterization of the catalyst after reaction at high conversion indicates that dispersed vanadia partly agglomerates into vanadia crystallites during methanol oxidation.

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Xanes and 51V Nmr study of vanadium-oxygen compounds

Cited by 55 publications

References 23 publications

Synthesis, Spectroscopic and Structural Studies on Vanadium(V) Periodates

Synthesis, Spectroscopic and Structural Studies on Vanadium(V) Periodates

Defective by design: vanadium-substituted iron oxide nanoarchitectures as cation-insertion hosts for electrochemical charge storage

Partial Oxidation of Methanol Over Highly Dispersed Vanadia Supported on Silica SBA-15

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