Preparation, Properties, and ESCA Characterization of Vanadium Surface Compounds on Silicagel. II

Horvath, B.; Strutz, Juergen; Geyer-Lippmann, J.; Horváth, Endre

doi:10.1002/zaac.19814831224

Cited by 18 publications

(9 citation statements)

References 11 publications

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“…This was ascribed to an electron-withdrawing effect of the Si02 support. 27 This results in a high ionicity of the Si-O to V bond; i.e., the Si-O ligands are highly electronegative. This latter property of the bonding in the V04 unit on the surface suggests that the lowest energetic excitation is localized in the short axial V-O bond, since the other three oxygens are not expected to release their electrons easily.…”

Section: Resultsmentioning

confidence: 99%

A luminescence spectroscopy study on supported vanadium and chromium oxide catalysts

Hazenkamp¹,

Blasse²

1992

J. Phys. Chem.

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The luminescence properties of dehydrated silica-and alumina-supported vanadium and chromium oxide catalysts at low loadings at 4.2 K are reported and discussed. It is shown that one luminescent oxc-vanadium (-chromium) species is present on silica surfaces and more than one species on alumina surfaces. The Cr/AIz03 sample does not show luminescence. The monomeric tetrahedral species show vibrational structure in their emission spectra, and their decay times amount to 10-30 ms. These luminescence properties are different from those of similar complexes in the solid state. The discrepancy is ascribed to a different electronic structure of the surface species which localizes the excited state in a short metal-oxygen bond.

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Section: Resultsmentioning

confidence: 99%

A luminescence spectroscopy study on supported vanadium and chromium oxide catalysts

Hazenkamp¹,

Blasse²

1992

J. Phys. Chem.

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“…Figure 5. Scheme of the experimental PECVD setup Nitrogen Gas Delivery Line: Nitrogen gas (Westfalen AG, 99.999%) was further purified by passing it through three separate catalytic columns (silica gel, molecular sieves, and an oxysorb catalyst [35] ), in order to remove traces of oxygen and moisture from the nitrogen stream.…”

Section: Methodsmentioning

confidence: 99%

Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta₂N₃

2004

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Keywords: Tantalum / Nitrides / Plasma-enhanced chemical vapor deposition / X-ray diffraction / Electron microscopy Microcrystalline tantalum nitride films were prepared on various substrates from TaCl 5 precursor and nitrogen gas using the plasma-enhanced chemical vapor deposition (PECVD) method. Syntheses carried out at 600−650°C led to single-phase samples of the tantalum nitride Ta 2 N 3 with a defect fluorite-type structure. The anion vacancies were found to order resulting in a 2 ϫ 2 ϫ 2 cubic superstructure of the C-Ln 2 O 3 type (space group Ia3 , Z = 16) with a = 9.8205(4) Å according to a Rietveld refinement of the X-ray IntroductionThe binary TaϪN system is quite rich in compounds with well-defined and variable stoichiometries. The formal oxidation state of tantalum covers the whole range from nearly zero to the maximum of ϩ5. These compounds can be divided into four groups: solid solutions of nitrogen in tantalum, the phase with the approximate stoichiometry Ta 2 N, three phases with a nearly 1:1 composition, and nitrogenrich nitrides. A few comprehensive reviews of tantalum nitride structural chemistry are available.[1Ϫ3] Results of the previous structural studies in this binary system are summarized in Table 1.Up to 5 at.% of nitrogen can be dissolved in the bodycentered cubic lattice of elemental tantalum, for example by heating of Ta powder in ammonia at 600Ϫ700°C.[3] The lattice constant of such solid solutions increases slightly to 3.315Ϫ3.369 Å compared to that of the pure metal (a ϭ 3.311 Å ). Observation of additional weak reflections suggests a cubic superstructure with the unit cell tripled in all directions and with a β ϭ 3a α ϭ 10.11 Å . The γ-phase with the composition range TaN 0.41Ϫ0.5 , also denoted as β-Ta 2 N, [4] crystallizes with a hexagonal unit cell.[1Ϫ4] Its crystal structure can be described as a hexagonal close packing of the tantalum atoms with the nitrogen atoms filling half of the octahedral interstices. While the earlier studies suggested a statistical distribution, [1,2] electron- [3] and neutron-diffraction [4] investigations revealed a trigonal P31m supercell with aЈ ϭ Ί3a, isostructural to β-Nb 2 N [14] and of the anti-Li 2 ZrF 6 -type.[15] The γ-phase can be obtained by nitriding of tantalum powder in gaseous ammonia at 800Ϫ900°C or from the elements at 2000°C. [1,3] The hexagonal ε-phase was proposed by Schoenberg [1] to have a B35 CoSn-type structure with the composition TaN 1.00 ; the same description was given by Brauer and Zapp.[2] In this structure type the nitrogen atoms are at the center of slightly distorted tantalum octahedra. Later, Christensen and Lebech [5] showed that the nitrogen atoms are displaced from these ideal positions reducing their coordination sphere to a square pyramid. The unit cell determined by Christensen and Lebech [5] (a ϭ 5.196 Å , c ϭ 2.911 Å ) is quite similar to that given by the other authors.[1Ϫ3] The ε-phase can be obtained as a product of nitriding of Ta powder at temperatures at Ͼ 1100°C. [1] Another modification of tantalum ...

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“…Figure shows high-resolution XPS core-level spectra of V 2p, Cu 2p, and Fe 2p for V/Fe, Cu/V/Fe, and Cu/Fe PBAs, respectively, and their deconvolution results using the Gaussian distribution fitting. The V 2p 3/2 peak can be fitted into three subpeaks at 516.0, 516.7, and 517.5 eV, corresponding to the V 3+ , V 4+ , and V 5+ , − respectively. The Cu 2p 3/2 peak is deconvoluted into two peaks centered at 933.0 and 935.6 eV for Cu 1+ and Cu 2+ , respectively.…”

Section: Resultsmentioning

confidence: 99%

Hierarchically Designed Cathodes Composed of Vanadium Hexacyanoferrate@Copper Hexacyanoferrate with Enhanced Cycling Stability

Choi

Baek

Lee

et al. 2020

ACS Appl. Mater. Interfaces

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Prussian blue analogues (PBAs) have been highlighted as electrode materials for aqueous rechargeable batteries (ARBs) because of their favorable crystal structure and electrochemical activity. However, dissolution of the transition-metal ions during cycling degrades the materials and hinders the development of long-life-span batteries. To overcome this limitation, a strategy to revive the capacity degradation of PBA-based cathodes was developed herein based on designing all-PBA-based core@shell materials, while specific reduction upon introducing the shell layers was minimized. The core@shell materials were constructed using a V/Fe PBA (high capacity) core and a Cu/Fe PBA (high cycling stability) shell via a two-step co-precipitation method. The electrochemical performances including specific capacity, cycling stability, and rate capability as a function of the Cu/Fe PBA shell thickness were explored. At the optimal Cu/Fe PBA thickness, improved capacity retention after 200 cycles of >90% (72% for the core only) was attained with negligible capacity reductions from 94 (core only) to 90 (core@shell) mA h g–1, arising from the high electrochemical activity and stability of the Cu/Fe PBA shell and stabilized interfaces due to the crystallographic coherence between the core and shell materials. In addition, the power performance of the core@shell materials was significantly improved, e.g., C38.4C/C0.6C for a core@shell of 80% and core only of 62%, arising from the unique chemical coordination and facile ion diffusion kinetics of the Cu/Fe PBA shell. The newly developed V/Fe@Cu/Fe PBA-based cathodes offer an effective strategy for fabricating sustainable and low-cost ARBs.

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Preparation, Properties, and ESCA Characterization of Vanadium Surface Compounds on Silicagel. II

Cited by 18 publications

References 11 publications

A luminescence spectroscopy study on supported vanadium and chromium oxide catalysts

A luminescence spectroscopy study on supported vanadium and chromium oxide catalysts

Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta₂N₃

Hierarchically Designed Cathodes Composed of Vanadium Hexacyanoferrate@Copper Hexacyanoferrate with Enhanced Cycling Stability

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Preparation, Properties, and ESCA Characterization of Vanadium Surface Compounds on Silicagel. II

Cited by 18 publications

References 11 publications

A luminescence spectroscopy study on supported vanadium and chromium oxide catalysts

A luminescence spectroscopy study on supported vanadium and chromium oxide catalysts

Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta2N3

Hierarchically Designed Cathodes Composed of Vanadium Hexacyanoferrate@Copper Hexacyanoferrate with Enhanced Cycling Stability

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Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta₂N₃