A NEXAFS determination of the oxidation state of vanadium carbide on V(110): observation of charge transfer from vanadium to carbon

Chen, J.G.; Kirn, C.M.; Frühberger, Bernd; DeVries, B.; Touvelle, M. S.

doi:10.1016/0039-6028(94)90035-3

Cited by 76 publications

(40 citation statements)

References 30 publications

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“…A similar line shape has been reported for bulk VO 2 [70,72,73]. Moreover, according to the correlation between the oxidation state and the L 3 -edge peak position of binary vanadium oxides, this resonance corresponds to the V 4+ state [74,75]. Indeed, Chen et al [74] reported that the V L 3 -edge position shifts by 0.7 eV per every ionic charge in the range from 515.5 eV (metallic vanadium) to 519.0 eV (V 2 O 5 ).…”

Section: In Situ Nap Xps Xanes and Tpr Studysupporting

confidence: 84%

“…Moreover, according to the correlation between the oxidation state and the L 3 -edge peak position of binary vanadium oxides, this resonance corresponds to the V 4+ state [74,75]. Indeed, Chen et al [74] reported that the V L 3 -edge position shifts by 0.7 eV per every ionic charge in the range from 515.5 eV (metallic vanadium) to 519.0 eV (V 2 O 5 ). In current study, the shift is aproximatelly 0.8 eV that corresponds to the partial reduction of V (Table 4) were at 459.0 eV, which is typical for bulk TiO 2 (Fig.…”

Section: In Situ Nap Xps Xanes and Tpr Studymentioning

confidence: 97%

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Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Каичев

Popova

Chesalov

et al. 2014

Journal of Catalysis

127

150

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address: vvk@catalysis.ru (V.V. Kaichev). A B S T R A C TThe methanol oxidation over highly dispersed vanadium oxide supported on TiO 2 (anatase) has been investigated by in situ Fourier transform infrared spectroscopy (FTIR), near ambient pressure X-ray photoelectron spectroscopy (NAP XPS), X-ray absorption near edge structure (XANES), and temperature-programmed reaction spectroscopy. The data were complimented with kinetics measurements in a flow reactor. It was found that at low temperatures dimethoxymethane competes with methyl formate, whereas the production of formaldehyde is greatly inhibited. FTIR shows the presence of non-dissociatively adsorbed molecules of methanol, as well as adsorbed methoxy, dioximethylene, and formate species under reaction conditions. According to the NAP XPS and XANES data, the reaction involves the reversible reduction of V 5+ cations, pointing that the vanadia lattice oxygen participates in the methanol oxidation through the classical Mars-van Krevelen mechanism. The detailed mechanism of the methanol oxidation on vanadia catalysts is discussed.

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Section: In Situ Nap Xps Xanes and Tpr Studysupporting

confidence: 84%

Section: In Situ Nap Xps Xanes and Tpr Studymentioning

confidence: 97%

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Каичев

Popova

Chesalov

et al. 2014

Journal of Catalysis

127

150

View full text Add to dashboard Cite

show abstract

“…Sn-metal chemistry absorption edge position of the species under investigation to the regression line (see, e.g. Chen et al, 1994, Mansour et al, 1994. In our case, this interpolation leads to a value of about 3.5 ± 0.2 for the oxidation state of the tin ions in chemically prepared Sn 3 N 4 .…”

Section: Snomentioning

confidence: 55%

XAFS investigations of tin nitrides

Lützenkirchen‐Hecht¹,

Scotti²,

Jacobs³

et al. 2001

J Synchrotron Radiat

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Tin nitrides (Sn3N4) prepared by the reaction of Sn-halides with KNH2 in liquid ammonia and a subsequent vacuum annealing procedure were investigated with transmission mode XAFS experiments. While the near edge data suggest the presence of a univalent Sn-compound with a valency close to +4, the analysis of the extended X-ray absorption fine structure proves the presence of two different local Sn sites in this crystal structure: While Sn(1) is surrounded by 4 nitrogen in a distance of 2.06 A, each Sn(2) ion is coordinated with 6 nitrogen at about 2.17 A radial distance.

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“…The carbon K-edge NEXAFS spectra (Figure 3) display the typical saturated hydrocarbon chain resonances arising from transitions to C-H and C-C antibonding molecular orbitals at 288.6 and 293 eV, respectively (St6hr, 1992). The weaker resonance at higher energy (~301 eV) is also attributed to transitions to C-C antibonding orbitals of long-chain alkane hydrocarbon molecules (Chen et al, 1994). Although the peak positions of these resonances remain constant among the three organoclays, the intensities vary and decrease in the order: C18H37SiC13-met >> C18H37Si(OMe)3-hex > C18H375iC13 -bex.…”

Section: Near-edge X-ray Absorption Fine Struoturementioning

confidence: 99%

Characterization of Montmorillonite Surfaces After Modification by Organosilane

Song

Sandı́

2001

Clays and clay miner.

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Abstract--X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), surface area measurements, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to examine the surface properties of organosilane-modified smectite-type aluminosilicate clays. Organic modified clays derived from the reactions of montmorillonite (containing 93-95% montmorillonite from a bentonite, <1% quartz, and 4-6% opal CT) with octadecyltrichlorosilane (C~sH37SiCI3) and octadecyltrimethoxysilane [CIsH37Si(OMe)3] are highly hydrophobic. Surface loadings of the modified clays depend on the organosilane and the solvent, and they range from 10 to 25 wt. %. The organic species are probably adsorbed to the outer surfaces and bound to the edges of the clay via condensation with edge-OH groups.Encapsulation of montmorillonite with CIsH37SiC13 and ClgH37Si(OMe)3 resulted in a hydrophobic coating that acts like a "cage" around the clay particles to limit diffusion. Basal spacings of the organic modified claysoremain at --15 A upon heating to 400~ in N2, whereas those of unmodified clays collapse to --10 A. A considerable reduction in surface area (by 75-90%) for organic modified clays is observed, which is consistent with the existence of a surface coating. The solvent used can affect the amount of organic silane coated on the clay particles, whereas the difference between the products prepared using C18H37SIC13 and ClsH37Si(OMe)3 in the same solvent is relatively small. The carbon and oxygen K-edge NEXAFS spectroscopy of the modified montmorillonite surfaces showed that surface coatings on the outside of the clay particles exist. The encapsulating system may allow for economical remediation and storage of hazardous materials.

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A NEXAFS determination of the oxidation state of vanadium carbide on V(110): observation of charge transfer from vanadium to carbon

Cited by 76 publications

References 30 publications

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

XAFS investigations of tin nitrides

Characterization of Montmorillonite Surfaces After Modification by Organosilane

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