Materials belonging to the CrVO4 structure type: preparation, crystal chemistry and physicochemical properties

Baran, Enrique J.

doi:10.1023/a:1004380530309

Cited by 62 publications

(68 citation statements)

References 128 publications

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“…All fundamental peaks can be indexed to the orthorhombic structure (space group Cmcm). The crystallographic parameters of VPO 4 powders, a=0.5238 nm, b=0.7790 nm, c=0.6288 nm, and cell volume=0.2566 nm 3 , are close to the literature data by conventional solid-state synthesis methods [21] . in the XRD profiles, indicating that Y was doped completely into the crystal lattice of LiVPO 4 F. Y doping does not change the crystal structure of LiVPO 4 F. Therefore, Y 3＋ ions may be located at V 3+ sites in the crystal lattice.…”

Section: Methodssupporting

confidence: 79%

Preparation and electrochemical studies of Y-doped LiVPO4F cathode materials for lithium-ion batteries

Zhong

Liu

et al. 2009

J. Wuhan Univ. Technol.-Mat. Sci. Edit.

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Y-doped LiVPO 4 F cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped LiVPO 4 F samples were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies show that the Y-doped LiVPO 4 F samples have the same triclinic structure as the undoped LiVPO 4 F. The Li extraction/insertion performances of Y-doped LiVPO 4 F samples were investigated through charge/discharge, cyclic voltammogram (CV) , and electrochemical impedance spectra(EIS). The optimal doping content of Y is x=0.04 in LiY x V 1 -x PO 4 F system. The Y-doped LiVPO 4 F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVPO 4 F cathode materials are attributed to the addition of Y 3+ ion by stabilizing the triclinic structure.

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Section: Methodssupporting

confidence: 79%

Preparation and electrochemical studies of Y-doped LiVPO4F cathode materials for lithium-ion batteries

Zhong

Liu

et al. 2009

J. Wuhan Univ. Technol.-Mat. Sci. Edit.

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“…35,36 In the breadth of this band for 10V12CrAl and 12Cr10VAl and in the absence of CrVO 4 , diffraction lines for these samples suggest that the CrVO 4 domains are disordered and highly dispersed. 27,[37][38][39] The 820 cm -1 band may reflect the presence of polychromates, polyvanadates, or mixed V-O-Cr oligomers, but its specific origin remains unclear. Figure 2 shows X-ray absorption near-edge spectroscopy (XANES) spectra for 10VAl, 12CrAl, 10V12CrAl, and 12Cr10VAl after treatment at 773 K for 2 h in flowing dry air and for three crystalline compounds V 2 O 5 , CrO 3 , Cr 2 O 3 .…”

Section: Resultsmentioning

confidence: 99%

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts

2006

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The structure and surface composition of binary oxides consisting of CrO x and VO x dispersed on alumina and their effects on the rate and selectivity of oxidative dehydrogenation (ODH) of propane were examined and compared with those for CrO x and VO x dispersed on alumina. VO x deposition on an equivalent CrO x monolayer on alumina and deposition of CrO x on an equivalent monolayer of VO x deposited on alumina led to CrVO 4 species during thermal treatment with concomitant reduction of Cr 6+ to Cr 3+ .

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“…A totally replaced CrPO4 showed only an amorphous phase even after the calcination at 973 K (i). Different hydrates of CrPO4 are known 52) ; their calcinations at high temperature allow the anhydrous material to be formed in two types of their polymorphic forms: β-CrPO4 above 1273 K and α-CrPO4 above 1448 K. Thus, amorphous CrPO4 is stable and does not crystallize even at high temperature of 1173 K in the DTA curves 25) . FT-IR spectra of CrV1-xPxO4 well correlated with the results of XRD analyses.…”

Section: Crv1 _ Xpxo4 Catalystsmentioning

confidence: 99%

Preparation of Crystalline CrVO<sub>4</sub> Catalyst by Soft Chemistry Technique and Application for Vapor-phase Oxidation of Picolines

Shishido

2011

J. Jpn. Petrol. Inst.

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A series of Cr _ V mixed oxide catalysts (CrVO4, Cr1-xAlxVO4 and CrV1-xPxO4) have been prepared by "soft chemistry" technique. By mixing the aqueous solution of the raw materials and controlling the pH value, chromium vanadates (CrVO4-I and III) were prepared as the pure orthovanadate crystalline form. Prepared chromium vanadates were employed in the vapor phase oxidation of 2-, 3-, and 4-picolines in order to investigate the relationship between the catalysis and structure of chromium vanadate. CrVO4-I (monoclinic) showed much higher activity than CrVO4-III (orthorhombic), suggesting that the bridging oxygen in the V _ O _ Cr bond is responsible for the catalytic activity. When a part of Cr or V was replaced with Al or P without changing the CrVO4-I type structure, the activities were enhanced. The acidity increased by the replacement of Cr with Al and V with P in CrVO4-I, resulting in the accelerating desorption of products. A partial replacement of V with P significantly improved activity and this is probably due to the modification of the redox properties of V _ O _ Cr site in addition to the accelerating desorption of products. An addition of large amount of steam in the reactants improved the yield of desired products. Both Lewis and Brønsted acid sites were detected on the surface of CrV0.95P0.05O4, and the number of the latter increased by the addition of steam. The enhanced activity by the addition of steam is interpreted by the fact that Brønsted acid sites are produced by the hydrolysis of V _ O _ Cr bond on the surface and activate picoline molecules by withdrawing the electrons of the pyridine ring, and at the same time, enable to accelerate the desorption of the acid products. Even in the absence of gaseous oxygen, the oxygenated products were formed, thus, a Mars and van Krevelen mechanism was suggested. KeywordsChromium vanadate catalyst, Soft chemistry, Picoline, Vapor phase oxidation, Brønsted acid site, Mars and van Krevelen mechanism viewed 21) recently. Shishido and co-workers have reported that CrVO4 prepared by "soft chemistry" technique in the pure crystalline form (CrVO4-I, monoclinic) is also active for the vapor phase oxidation of picolines 22)～26) . In this article, the characterization of Cr _ V mixed oxide catalysts by using XRD, FT-IR, TG-DTA, NH3-TPD, Raman, and TPR techniques, and their catalysis in vapor phase oxidations of 2-, 3-and 4-picolines are demonstrated. The correlation between surface structure and catalytic behavior of a series of Cr _ V mixed oxide catalysts prepared by "soft chemistry" technique are briefly reviewed. Experimental 1. Catalyst PreparationA series of CrVO4, Cr1-xAlxVO4 (x 0.25, 0.5, 0.75 and 1.0) and CrV1-xPxO4 (x 0.02-1.00) catalysts were prepared following method proposed by Touboul and co-workers 27),28) . Aqueous solutions of NH4VO3, Cr(NO3)3 9H2O, Al(NO3)3 9H2O and NH4H2PO4 were mixed and the pH value of the solution was lowered below 1.0 to form homogeneous solution by adding 3 M (1 M 1 mol ・dm -3 ) nitric acid. Then, the pH value of the solution...

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Materials belonging to the CrVO4 structure type: preparation, crystal chemistry and physicochemical properties

Cited by 62 publications

References 128 publications

Preparation and electrochemical studies of Y-doped LiVPO4F cathode materials for lithium-ion batteries

Preparation and electrochemical studies of Y-doped LiVPO4F cathode materials for lithium-ion batteries

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts

Preparation of Crystalline CrVO<sub>4</sub> Catalyst by Soft Chemistry Technique and Application for Vapor-phase Oxidation of Picolines

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Materials belonging to the CrVO4 structure type: preparation, crystal chemistry and physicochemical properties

Cited by 62 publications

References 128 publications

Preparation and electrochemical studies of Y-doped LiVPO4F cathode materials for lithium-ion batteries

Preparation and electrochemical studies of Y-doped LiVPO4F cathode materials for lithium-ion batteries

Nature, Density, and Catalytic Role of Exposed Species on Dispersed VOx/CrOx/Al2O3 Catalysts

Preparation of Crystalline CrVO<sub>4</sub> Catalyst by Soft Chemistry Technique and Application for Vapor-phase Oxidation of Picolines

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Nature, Density, and Catalytic Role of Exposed Species on Dispersed VO_x/CrO_x/Al₂O₃ Catalysts