Synthesis of Vanadium Oxide Nanofibers with Variable Crystallinity and V⁵⁺/V⁴⁺ Ratios

Abstract

Tailoring the morphological, chemical, and physical properties of vanadium oxides (VOx) is crucial to optimize their performance in current and future applications. The present contribution proposes a new route to obtain VOx nanofibers with different V 4+ /V 5+ ratios and crystallinity. The method involves the exclusive electrospinning of water-free NH 4 VO 3 -saturated solutions including a reductant. Subsequent air-annealing under suitable conditions yields vanadium oxide fibers of 20–90 nm diameter and 10–50 m 2 /g surface area. The presence of the reductant gives rise to VOx nanofibers with a considerable proportion of V 4+ . Then, the right choice of the calcination heating rate and temperature permits to modify the V 4+ /V 5+ ratio as well as the crystalline phase and crystallite size of the fibers. With the proposed methodology, long-range continuous single-phase orthorhombic V 2 O 5 and monoclinic V 3 O 7 nanofibers are obtained.

A review of Raman spectroscopy of vanadium oxides

“…The lines at 425 and 494 cm −1 might also be associated with V 4 O 9 , whereas the remaining bands should correspond to the signal from V 3 O 7 . The spectra of our samples are remarkably similar to those reported earlier for V 7 O 16 (Figure d), V 6 O 13 (Figure e), and the product of degradation of some samples (Figures b and a) . Therefore, we believe that V 3 O 7 was produced in all the disputable cases.…”

“…Although V 3 O 7 occupies much of the phase diagram, there are few reports of its formation. Recently, it has been produced in a form of nanofibers and nanoflowers . Raman scattering for the samples has been reported (Figure a,b).…”

“…Raman scattering in (a) V 3 O 7 nanofibers, (b) V 3 O 7 nanoflowers, and (c) V 3.047 O 7 [Colour figure can be viewed at wileyonlinelibrary.com]…”

Selective Oxidation of Simple Aromatics Catalyzed by Nano-Biomimetic Metal Oxide Catalysts: A Mini Review

“…The porous property observed in these Fe/Cu/V nano-catalysts contributed to the improvement of benzene oxidation efficiency using H 2 O 2(aq) with additional H 2 O proportions in CH 3 CN (Ramu et al, 2017;Wanna et al, 2019b), which is consistent with the effect of water-assisted benzene oxidation catalyzed by the molecular iron complex encapsulated in the zeolite (Yamaguchi et al, 2015). In addition, the powder XRD and selected area (electron) diffraction SAD-TEM analysis for V nr catalyst indicated that the crystal grew longer to rod shape with preferential (220) orientation that can be crucial for the related additional activities (Berenguer et al, 2017). The crystalline feature of Fe and Cu catalysts also exhibited a distinctive crystal arrangement that directly corresponded to the nature of the parental metal-oxide materials.…”

Metal-Organic Decomposition-Mediated Nanoparticulate Vanadium Oxide Hole Transporting Buffer Layer for Polymer Bulk-Heterojunction Solar Cells

“…The V 2p XPS spectrum was characterized to understand the surface oxidation state of the V 2 O 5 films ( Figure 2 b) with the Al Kα X-ray. The strong peak at the binding energy of 517 eV, which was assigned to the V 5+ of V 2 O 5 , was observed in both the bare V 2 O 5 and the NP-V 2 O 5 prepared using 40 mM PEG [ 38 , 39 , 40 ]. No significant changes in the XRD and XPS spectra were observed between the bare V 2 O 5 and NP-V 2 O 5 layers.…”