Investigations on Diffuse Reflectance Spectra of V<sub>2</sub>O<sub>5</sub> Powder

Karvaly, Béla; Hevesi, I.

doi:10.1515/zna-1971-0211

Cited by 70 publications

(18 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The edge energy, or in other words the band-gap energy of V 2 O 5 crystallites, is 2.3 eV in this work, in good agreement with the literature value of 2.3-2.4 eV. [40][41][42] From the results in Table 4, it is concluded that three major factors affect the edge energy of the V(V) cations, as discussed below:…”

Section: Bulk Compositions Andsupporting

confidence: 90%

In Situ Spectroscopic Investigation of Molecular Structures of Highly Dispersed Vanadium Oxide on Silica under Various Conditions

et al. 1998

View full text Add to dashboard Cite

The molecularly dispersed V 2 O 5 /SiO 2 supported oxides were prepared by the incipient wetness impregnation of 2-propanol solutions of V-isopropoxide. The experimental maximum dispersion of surface vanadium oxide species on SiO 2 was achieved at ∼12 wt % V 2 O 5 (∼2.6 V atoms/nm 2 ). The surface structures of the molecularly dispersed V 2 O 5 /SiO 2 samples under various conditions were extensively investigated by in situ Raman, UVvis-NIR DRS and XANES spectroscopies. The combined characterization techniques revealed that in the dehydrated state only isolated VO 4 species are present on the silica surface up to monolayer coverage. Interestingly, the three-member siloxane rings on the silica surface appear to be the most favorable sites for anchoring the isolated, three-legged (SiO) 3 VdO species. Hydration dramatically changes the molecular structure of the surface vanadium oxide species. The specific structure of the hydrated surface vanadium oxide species is dependent on the degree of hydration. The molecular structure of the fully hydrated vanadium oxide species closely resembles V 2 O 5 ‚nH 2 O gels, rather than V 2 O 5 crystallites. The fully hydrated surface vanadium oxide species are proposed to be chain and/or two-dimensional polymers with highly distorted square-pyramidal VO 5 connected by V-OH-V bridges, which are stabilized on the silica surface by the sixth neighbor of Si-OH hydroxyls via Si-OH‚‚‚V hydrogen bonds. In analogy to the hydration process, alcoholysis occurs during methanol chemisorption, and similar molecular structures are proposed to interpret the interaction between methanol molecules and the surface vanadium oxide species on silica.

show abstract

Section: Bulk Compositions Andsupporting

confidence: 90%

In Situ Spectroscopic Investigation of Molecular Structures of Highly Dispersed Vanadium Oxide on Silica under Various Conditions

et al. 1998

View full text Add to dashboard Cite

show abstract

“…Figure 2 B shows plots of the modified Kubelka-Munk function versus the photon energy, from which the band-gap energies can be obtained. [33] The band-gap energy for TiO 2ÀX N X can be seen to be 2.95 eV, corresponding to the visible-light region, whereas that for undoped TiO 2 is 3.2 eV.…”

Section: Resultsmentioning

confidence: 96%

Mechanistic Studies of the Photocatalytic Oxidation of Trichloroethylene with Visible‐Light‐Driven N‐Doped TiO₂ Photocatalysts

Joung

Amemiya

Murabayashi

et al. 2006

Chemistry A European J

145

View full text Add to dashboard Cite

Visible-light-driven TiO2 photocatalysts doped with nitrogen have been prepared as powders and thin films in a cylindrical tubular furnace under a stream of ammonia gas. The photocatalysts thus obtained were found to have a band-gap energy of 2.95 eV. Electron spin resonance (ESR) under irradiation with visible light (lambda > or = 430 nm) afforded the increase in intensity in the visible-light region. The concentration of trapped holes was about fourfold higher than that of trapped electrons. Nitrogen-doped TiO2 has been used to investigate mechanistically the photocatalytic oxidation of trichloroethylene (TCE) under irradiation with visible light (lambda > or = 420 nm). Cl and O radicals, which contribute significantly to the generation of dichloroacetyl chloride (DCAC) in the photocatalytic oxidation of TCE under UV irradiation, were found to be deactivated under irradiation with visible light. As the main by-product, only phosgene was detected in the photocatalytic oxidation of TCE under irradiation with visible light. Thus, the reaction mechanism of TCE photooxidation under irradiation with visible light clearly differs markedly from that under UV irradiation. Based on the results of the present study, we propose a new reaction mechanism and adsorbed species for the photocatalytic oxidation of TCE under irradiation with visible light. The energy band for TiO2 by doping with nitrogen may involve an isolated band above the valence band.

show abstract

“…Diffuse reflectance spectra were measured relative to corundum (Hoechst Ceram Tec) with a Shimadzu Model 3101 spectrophotometer equipped with an integrating sphere unit. The onset of the lowest energy transition E on was determined according to the method by Karvaly and Hevesi [60] as described previously. [2a] Cyclic voltammetry was performed with an EG&G Princeton Applied Research Model 264A potentiostat by using a conventional three-electrode assembly consisting of a glassy-carbon working electrode, a platinum wire as counter electrode, and an Ag/AgCl reference electrode in saturated KCl solution.…”

Section: Methodsmentioning

confidence: 99%

Chiral Metal-Dithiolene/Viologen Ion Pairs: Synthesis and Electrical Conductivity

et al. 2001

View full text Add to dashboard Cite

Enantiomerically pure dithiolene complexes NBu4[Ni[(R,R)-diotte)2] and NBu4[Ni((S,S)-diotte]2] (diotte2- = a 1,3-dioxolane-tetrathiaethylene), were prepared from the corresponding enantiomers of a diotte2- precursor. The structure of the precursor was solved by single-crystal X-ray analysis; desulfurization afforded a novel tetrathiafulvalene derivative. Combination of the complex monoanion with the enantiomers of the viologen derivative bis(2-methyl-3-hydroxypropyl)-4,4'-dipyridinium (HiBV2+) afforded enantiomeric and diastereomeric ion-pair complexes of the type HiBV[Ni(diotte)2]2. For comparison, the analogous compounds A[Ni(diotte)2]2, (A2+ = methyl (MV2+), octyl (OV2-), stearyl (StV2+) viologen or two 2,2'-bipyridinium acceptors), HiBV-[Ni(diotte)L] [L = mnt2- (maleonitrile-1,2-dithiolate), dmit2- (2-thioxo-1,3-dithiol-4,5-dithiolate)], MV[Ni(dmit)2)]2, [Ni(diotte)2], and [Ni(diotte)(dmit)] were synthesized. An X-ray powder diffraction structural analysis of MV-[Ni(dmit)2)]2 revealed the presence of mixed stacks that contain the sequence anion-anion-cation. While no short contacts are observable within a stack, these are observed between the stacks for the dication-anion interaction by short S...H distances in the range of 2.77 to 2.86 A, and for the anion-anion interaction short S...S distances of 3.55 to 3.65 A. In agreement with the absence of intrastack interactions, no ion-pair charge-transfer band can be detected in this and the other complexes. ESR and UV/Vis data suggest that in [Ni(diotte)2]- electron delocalization is less pronounced than in the corresponding mnt2- and dmit2- complexes. The specific electrical conductivity (sigma) of pressed powder pellets ranges from 10(-2) to 10(-12) ohm(-1) cm(-1) and in all cases increases with increasing temperature (293 - 393 K) according to an Arrhenius law. Corresponding activation energies vary from 0.14 to 0.93 eV and increase linearly with log a for structurally similar ion pairs. Charge generation is postulated to occur by disproportionation of the monoanion as suggested by the almost linear increase of log(sigma) with decreasing disproportionation energy. The conductivity of diastereomers of ions with two unlike configurations like [(S,S)-HiBV]-[Ni[(R,R)-diotte]2]2 (1.1 x 10(-1) ohm(-1) cm(-1)) is one to two orders of magnitude higher as compared to the diastereomers with two like-configured ions.

show abstract

Investigations on Diffuse Reflectance Spectra of V₂O₅ Powder

Cited by 70 publications

References 0 publications

In Situ Spectroscopic Investigation of Molecular Structures of Highly Dispersed Vanadium Oxide on Silica under Various Conditions

In Situ Spectroscopic Investigation of Molecular Structures of Highly Dispersed Vanadium Oxide on Silica under Various Conditions

Mechanistic Studies of the Photocatalytic Oxidation of Trichloroethylene with Visible‐Light‐Driven N‐Doped TiO₂ Photocatalysts

Chiral Metal-Dithiolene/Viologen Ion Pairs: Synthesis and Electrical Conductivity

Contact Info

Product

Resources

About

Investigations on Diffuse Reflectance Spectra of V2O5 Powder

Cited by 70 publications

References 0 publications

In Situ Spectroscopic Investigation of Molecular Structures of Highly Dispersed Vanadium Oxide on Silica under Various Conditions

In Situ Spectroscopic Investigation of Molecular Structures of Highly Dispersed Vanadium Oxide on Silica under Various Conditions

Mechanistic Studies of the Photocatalytic Oxidation of Trichloroethylene with Visible‐Light‐Driven N‐Doped TiO2 Photocatalysts

Chiral Metal-Dithiolene/Viologen Ion Pairs: Synthesis and Electrical Conductivity

Contact Info

Product

Resources

About

Investigations on Diffuse Reflectance Spectra of V₂O₅ Powder

Mechanistic Studies of the Photocatalytic Oxidation of Trichloroethylene with Visible‐Light‐Driven N‐Doped TiO₂ Photocatalysts