Vanadium oxide nanoparticles

Guimond S, Haija MA-A, Kaya S, Lu J, Wdssemieder J, Shaikhutdinov S. K et al. (2006). Vanadimn oxide siufaces and supported vanadium oxide nanoparticles. Top Catal, 38, 117 Jochum W, Penner S, Kramer R, Fottinger K, Rupprechter G, Klotzer B (2008). Defect formation and water-gas shift activity on polycrystaUine P-Ga O. J Catal, 256, 278... 

Supported vanadium oxide nanoparticles effect of preparation method, support and type of precursor on the catalytic performances in the ODH of methanol to formaldehyde... 

Supported vanadium oxide nanoparticles effect of preparation method.. 

Self-assembled nanorods of vanadium oxide bundles were synthesized by treating bulk V2O5 with high intensity ultrasound [34]. By prolonging the duration of ultrasound irradiation, uniform, well defined shapes and surface structures and smaller size of nanorod vanadium oxide bundles were obtained. Three steps which occur in sequence have been proposed for the self-assembly of nanorods into bundles (1) Formation of V2O5 nuclei due to the ultrasound induced dissolution and a further oriented attachment causes the formation of nanorods (2) Side-by-side attachment of individual nanorods to assemble into nanorods (3) Instability of the self-assembled V2O5 nanorod bundles lead to the formation of V2O5 primary nanoparticles. It is also believed that such nanorods are more active for n-butane oxidation. 

So far, only two reports have been found in the literature on the syntheses of V2O3 and VO2 nanoparticles [6,9]. The purpose of this article is to study the probability of preparation of V2O3, VO2 and V2O5 nanopowders by pyrolysis of the precursor, (NH4)5 [(VO) 6 (C03)4(0H)9] IOH2O, at lower temperatures under H2, N2 or air atmosphere respectively. Our investigation is aimed to prepare the ceramics of vanadium oxides with nanometer-sized grains using these powders and to observe the... 

When the formation of V-oxide nanoparticles starts, the selectivity to benzaldehyde decreases considerably due to faster consecutive oxidation. Both the loading of vanadium and the nature of the zeolite influence the formation of these V-oxide nanoparticles. The inner surface area of zeolites is very high (up to 1000 mVg as in the case of Vx-HCM samples see Table 1), and thus the formation of V-oxide nanoparticles starts much below the vanadium loading necessary for the formation of a monolayer (around 10% wt. for a surface area of... 

If the reaction occurs in the boundary region, the nanoparticles acquire a form of nanotubes, nanorods and alike [249]. For instance, sonochemical synthesis of the vanadium oxide nanorods by treating bulk V2O5 with high intensity sonochemical technique has been described in [252]. 

Fig. 7.5 Surface vanadium oxide species occurring on supported vanadium oxide catalysts. Reproduced from [42] with permission of Elsevier, a Isolated surface VO4 species, b Polymeric surface VO4 species, c Crystalline V2O5 nanoparticles above monolayer surface coverage...

The preparation of hybrid materials based on BC comprises a limited number of inorganic nanoparticles (NPs) such as a few metals (silver [211-231], selenium [214, 232-234], gold [223, 224, 235], nickel [236, 237], platinum [210] and palladium/cop-per [238]), metal oxides (silica [239-247], titanium oxide [242, 248-255], iron oxides [209, 221, 256-267], zinc oxide [268-270], vanadium oxide [254]), calcium phosphate... 

Figure 17.12. The supported vanadium oxide phase under ambient conditions in commercial o-xylene catalysts is present both as dispersed surface VOx species (broad Raman band from 900-l, 000 cm for 0.7 and 1.4% V205/Ti02) and crystaltine V2O5 nanoparticles (sharp Raman band at 994 cm for 2.0 and 3.0% V205/Ti02). Reprinted from Wachs, I., Saleh, R., Chan, S., Chersich, C. (1985). Appl. Catal., 15, p. 339, copyright 1985 from Elsevier.

Ionic liquid assisted vanadium pentoxide, zinc oxide and cobalt oxide nanoparticles... 

In addition to the above, preparation in w/o microemulsions of nanoparticles of various other types of compounds, viz. silica-coated iron oxide, Fe203-Ag nanocomposite, oxides of ytrium, erbium, neodymium, vanadium and cobalt, titanates of barium and lead, ferrites of barium, strontium, manganese, cobalt and zinc, oxide superconductors, aluminates, zirconium silicate, barium tungstate, phosphates of calcium, aluminium and zinc, carbonates of calcium and barium, sulphides of molybdenum and sodium, selenides of cadmium and silver etc. have been reported. Preparative sources and related elaboration can be found in [24]. 

A variety of other nanoparticles have been formed by such in situ sol-gel reactions. Examples are the oxides of titanium, aluminum, - tanta-lum, zirconium, niobium, and vanadium. Some nanocomposites of this type have also included barium titanate, calcium oxide, calcium salts, borates, HTiNbOg, and Eu dopants. ... 

This system typically uses sulfuric acid as the electrolyte with a proton exchange membrane. While a porous separator could be used, for high efficiency operation, ion-selective membranes are generally preferred as vanadium crossover leads to losses in coulombic efficiency. At present, Nafion is the membrane of choice as V(V) is a powerful oxidizing agent, which can attack cheaper hydrocarbon-based ion selective membranes [21]. The redox reactions of different vanadium species have displayed reversibility and high activity on carbon based electrodes. Moreover, Li et al. discovered the catalytic effects of bismuth nanoparticles on V(II)/V(III) [51] and of niobium oxide nanorods on both V(II)Af(lII) and V(IV)Af(V) [52], which have been shown to further enhance the energy efficiency of the VRB by more than 10 %. 

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