Vanadium Oxide Nanotubes Research Articles

Hierarchical amorphous vanadium oxide and carbon nanotubes microspheres with strong interface interaction for Superior performance aqueous Zinc-ion batteries

Aqueous zinc-ion batteries have attracted more and more attention due to their safety, environmental benignity and high theoretical capacity. However, the lack of appropriate cathode materials with high capacity and long cycle life have become an obstacle to the development of aqueous zinc-ion batteries. Herein, the hierarchical amorphous vanadium oxide and carbon nanotubes (a-V2O5@CNTs) microspheres with strong interface interaction were successfully prepared by combing facile spray drying technique with annealing treatment. Benefiting from the a-V2O5 amorphous characters, CNTs framework high conductivity and hierarchical microspheres with strong interface interaction, the a-V2O5@CNTs exhibited abundant active sites, fast reaction kinetics as well as eminent structure stability. As a promising electrode material, the a-V2O5@CNTs displayed high specific capacity (480 mAh g−1 at 0.5 A g−1), good rate capability and long-term stability under high current density (158 mAh g−1 at 30 A g−1 over 1000 cycles). Meanwhile, the corresponding mechanism was further illustrated through different characterizations. Furthermore, the as-assembled flexible pouch battery based on the a-V2O5@CNTs delivered outstanding flexibility and feasibility. Hence, this work provides a new idea for developing high performance cathode materials of aqueous zinc-ion batteries.

Multi-walled vanadium oxide nanotubes modified 3D microporous bioderived carbon as novel electrodes for hybrid capacitive deionization

Herein, a promising rationally-designed, high surface area multi-walled vanadium oxide nanotubes (VOx NTs) with a large interlayer spacing (6.5 Å) has been demonstrated as a cathodic dopant for efficient hybrid capacitive deionization (c-HCDI). The VOx NTs enhanced the surface charge of the 3D microporous graphene-like carbon, derived from natural palm tree (CNPT), as verified by Raman profiles and potential of zero charge measurements. The CDI batch-fashion testing has been performed using large surface area electrodes (6 × 7 cm2) and 135 ml of saline NaCl electrolyte. Interestingly, the used c-HCDI showed high salt adsorption capacity (SAC) of 25.0 mg/g for 6 mM NaCl at 1.6 V compared to the symmetric capacitive deionization configuration (s-CDI) that is only sustaining 16.0 mg/g. Besides, the cell demonstrates efficient stable SAC regardless of the initial feed concentration (1.6–25 mM) of NaCl. The charge efficiency of the c-HCDI markedly raised by around 25% over s-CDI for 5 mM NaCl, indicating the improved permselective manner of sodium ion diffusion/intercalation at the VOx NTs/CNPT cathode. Most importantly, the c-HCDI demonstrates a superior salt adsorption retention of 94.7% after 50 successive charge/discharge cycles compared to s-CDI that showed a decline of 7% after only 15 cycles. The Improved surface charge and wettability together with the pseudocapacitive storage manner of the cathode composite illustrate the synergism obtained via the hybrid configuration..

Fast Zn2+ kinetics of vanadium oxide nanotubes in high-performance rechargeable zinc-ion batteries

Mild aqueous rechargeable Zn-ion batteries emerge as potential grid energy storage devices due to excellent cycling stability, high Coulombic efficiency and low cost. However, reliable cathodes with high rate capability still need to be optimized. Previous vanadium oxide cathodes generally show the mechanism of Zn2+ intercalation into crystal layers, during which the lattice structure of active materials keeps stable. Different from this intercalation mechanism, here, we report a special conversion mechanism of Zn2+ storage. Vanadium oxide nanotubes with interlaminar dodecylamine are employed as the cathode. During the initial activation process, the cathode is fully converted to layered zinc pyrovanadate with amorphous zones induced by protonated dodecylamine, while the discharge process results in reversible formation of an amorphous-phase product during cycling. Layered zinc pyrovanadate can be electrochemically recovered from the amorphous phase after the Zn2+ de-intercalation. Despite an armorphous phase as the discharge product, this active material shows high cycling stability and fast Zn2+ kinetics. In addition, this cathode displays a specific energy density of ~242.5 Wh kg−1 and shows capacity retention of 80.5% after 950 cycles at 2.4 A g−1. Even at a high current density of 9.6 A g−1, the cathode delivers a specific energy of ~50 Wh kg−1 (5460 W kg−1) in 33 s. Although vanadium oxide nanotubes with interlaminar dodecylamine ions show little success in Li/Na-ion batteries with non-aqueous electrolytes, a mild aqueous Zn-ion system rejuvenates this material.

Aging effect on vanadium oxide hybrid nanotubes

Vanadium oxides present a rich magnetic phase diagram depending on the oxidation state of the V ions. In particular the vanadium oxide nanotubes (VOx NTs) present several promising perspectives for different technological applications for which it is essential to know the oxidation state of V ions, as well as to evaluate the stability with the aging time of the tubes. In this work we present a systematic study of the time evolution of the magnetic properties of VOx NTs. For this complete characterization, we used electron spin resonance (ESR) and dc-susceptibility techniques, which were supplemented with TEM microscopy and XANES. We observed that for aging in normal environmental conditions of pressure, temperature and humidity, the V4+ ions oxidize to V5+ . Although the multiwall tubular structure is maintained, this oxidation process produces a marked change in the magnetic properties. We conclude that the aging of the samples affects the V4+ /V5+ relationship in the VOx NTs, which may contribute to explain the significant dispersion of data reported in the bibliography.

NaV2O5 from Sodium Ion-Exchanged Vanadium Oxide Nanotubes and Its Efficient Reversible Lithiation as a Li-Ion Anode Material

Efficient synthetic protocols for stable oxide materials as Li-ion battery electrodes are important not only for improving long-term battery performance but also for tackling potential material abu...

Ammonium hexadeca-oxo-heptavanadate microsquares. A new member in the family of the V7O16 mixed-valence nanostructures

This paper presents the new mixed valence heptavanadate (NH4)2V7O16 micro squares, a further but carbonless member of the vanadium oxide nanotubes and nanourchins family, where ammonium ions replace the long carbon chain amines.

Bio-additive fuels from glycerol acetalization over metals-containing vanadium oxide nanotubes (MeVOx-NT in which, Me = Ni, Co, or Pt)

The biodiesel production has led to a drastic surplus of glycerol and catalytic conversion of glycerol into value-added products is of great industrial importance. Thus, the acetalization of glycerol with ketone or aldehydes allows the glycerol transformation into bio–additive fuels. In this work, metals-containing vanadium oxides nanotubes (MeVOx NT in which, Me = Co, Pt or Ni) have been synthesized with additional internal porosity and tested in the acetalization of glycerol with acetone (AG) for valuable biofuels production. The catalysts showed remarkable performances in the AG reaction. Furthermore, by variation of the composition, catalyst loading and temperature and using distinct substrates (butyraldehyde, furfuraldehyde and benzaldehyde), NiVOxNT is active, being very selective to solketal and reciclable for 4 times in the AG reaction. On the contrary, pure VOx NT easily deactivated due to the structure agent removal during the reaction, which promote the collapse of the tubular structure. The CoVOxNT and PtVOxNT catalysts did not exhibit such a stable structure and easily deactivated in the reaction due to leaching of the metals oxides during the AG.

Structural Evolution during Lithium- and Magnesium-Ion Intercalation in Vanadium Oxide Nanotube Electrodes for Battery Applications

Multiwalled vanadium oxide nanotubes are an intriguing class of materials due to their complex and functional structure. They have especially gained attention as an electrode material for rechargeable ion batteries exhibiting Li-ion storage capacities up to 250 mAh/g. The pristine nanotube materials and their electrochemical properties have previously been investigated extensively; however little knowledge exists on the structural transformations induced by ion storage in vanadium oxide nanotube electrodes. In this work, the changes in the atomic-scale and nanoscale structure during lithium- and magnesium-ion storage in two types of vanadium oxide nanotubes are investigated by operando powder X-ray diffraction and total X-ray scattering. Linear expansion and contraction of the VOx layers with vanadium reduction and oxidation are observed, while the interlayer spacing is found to be drastically dependent on the nature of the templating molecules or ions residing in the interlayer space of the pristine tube...

Hydrogen storage comparison of M doped vanadium oxide nanotubes (M = Mo, Zr and W): A molecular simulation study

Zr, Mo and W doped Vanadium oxide nanotube were considered as remarkable materials for hydrogen storage applications. Monte Carlo molecular simulation was performed to study the adsorption behavior of hydrogen molecules on Vanadium oxide nanotubes (VONTs). The effects of temperature, pressure and mole percent of hydrogen on adsorption capacity of VONTs were investigated to provide deep insight of adsorption behavior. The results represented that hydrogen adsorption is an increasing function of pressure and at about 50 MPa all three metal doped VONT has maximum hydrogen capacity. At 5 MPa and room temperature, the hydrogen capacities of Mo, W and Zr doped VONTs were 1.39, 0.88 and 1.43 w% respectively. With temperature increment up to room temperature, more reduction in initial hydrogen capacity were observed in Mo and Zr doped VONTs.Evaluating hydrogen adsorption of Zr doped VONT from pure and hydrogen /nitrogen mixtures at 300 K indicated that under 2 Mpa, modifications in adsorption capacities were insignificant after N2 addition to the environment. Therefore, Zr doped VONT in hydrogen /nitrogen mixture environment can act as a capable adsorbent for Hydrogen storage system in comparison with Mo and W doped VONTs.

Synthesis and Characterization of Zr-Doped Vanadium Oxide Nanotubes

In this research study for the firsttime zirconium doped vanadium oxide nanotubes (VONTs) were synthesized. Zr-doped VONTs were performed by using hydrothermal method. Zr-VONTs prepared 0.02 wt%. The structure and morphology of the nanotubes were investigated by x- ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In contrast to the undoped VONTs, the interlayer distance between oxide layers in the (V_0.98Zr_0.02 ) _x ONTs increases owing to replacement of some V in nanotubes by Zr with a large ionic radius. The results showed that zirconium 0.02wt% doped VONTs complately and the doping Zr into VONTs leads to increasing interlayer distances.

Large interlayer spacing vanadium oxide nanotubes as cathodes for high performance sodium ion batteries.

Sodium ion batteries (SIBs), as a potential alternative to Li-ion batteries (LIBs), have attracted great attention from researchers. Herein, large interlayer spacing ferric ion substituted vanadium oxide nanotubes (Fe-VNTs) are fabricated using dodecylamine as a template via a facile hydrothermal treatment followed by a ferric ion substitution process. The distances between the adjacent layers of VNT, Fe-VNTs and orthorhombic V2O5 are 2.7 nm, 1.2 nm and 0.44 nm, respectively. The larger interlamellar spacing results in faster Na+ diffusion reaction kinetics, and the insertion of ferric ion into vanadium oxide layers removes the organic templates between the vanadium oxide layers, leading to high conductivity and small electrochemical reaction resistance. Serving as the sodium ion battery cathode, Fe-VNTs display enhanced sodium storage performance over orthorhombic V2O5.

Metal cations doped vanadium oxide nanotubes: Synthesis, electronic structure, and gas sensing properties

The potential sensor materials of scroll-like dodecylamine-templated vanadium oxide VOx nanotubes doped with Co2+ or Fe3+ have been prepared using a sol-gel technique followed by the hydrothermal treatment. The resultant samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning and transmission electron microscopies, thermal and elemental analysis. The gas sensing properties of the metal cations doped VOx nanotubes have been tested in the wide range of working temperatures and targets’ concentrations towards ammonia, ethanol, methanol, toluene and acetone. The highest sensor activity was revealed for ethanol. Stability and electronic properties of pristine and metal doped VOx layers as well as their ad-complexes with O2 as intermediates during the working process of a sensor were studied by DFT calculations. The study suggests two different mechanisms of cations' action on sensing properties of a VOx compound. In absence of steric obstacles, Co2+ doing is predicted to be the most efficient dopants for beneficial activation of VOx sensing properties.

Hydrogen adsorption capacity of vanadium oxide nanotube from pure and mixture gas environment through molecular simulation

ABSTRACTThe effects of temperature and pressure on the adsorption capacity of vanadium oxide nanotube (VONT) were investigated by Monte Carlo (MC) simulation. Hydrogen adsorption was an increasing function of pressure and in about 50 MPa VONT showed the maximum total hydrogen capacity of 5.17, 4.67 and 4.56 wt%. at 250, 275 and 300 K, respectively. On increasing the temperature to room temperature, 75% decrease in the initial adsorption capacity was observed.Appraising adsorption of the same number of hydrogen molecules from pure and hydrogen/nitrogen mixture at 300 K indicated that under 10 MPa, changes in adsorption capacities were inconsequential after N2 addition to the environment.

Synthesis and lithium storage properties of vanadium oxide nanotubes (VOxNTs)-Polyaniline nanocomposite as cathode material for lithium ion batteries

A novel VOxNTs-Polyaniline nanocomposite was prepared by hydrothermal treatment and a wet-chemistry method. When this VOxNTs-Polyaniline was used as cathode material for lithium ion batteries (LIBs), it displayed much higher specific capacity and better cycling stability compared with the pristine VOxNTs. The improvement of electrochemical performance could be attributed to the effective removal of a large part of organic template without any electrochemical activity by cationic exchange process and the incorporation of polyaniline with good conductivity as well as lithium storage property in itself via chemical oxidative polymerization. Moreover, the polyaniline could also behave as a useful structural buffer, alleviating the strain during repeated Li+ intercalation/deintercalation and contributing to cyclic stability. It is hopeful to further improve its performance through the complete elimination of useless soft-template and increasing the crystallinity of active VOx, making this novel VOxNTs-Polyaniline a promising cathode candidate with high performance for LIBs.

Fabrication of polypyrrole/vanadium oxide nanotube composite with enhanced electrochemical performance as cathode in rechargeable batteries

Vanadium oxide nanotubes (VOxNTs) with hollow as well as multi-walled features were fabricated under hydrothermal condition by soft-template method. This novel VOxNTs can be used as cathode material for lithium ion batteries (LIBs), but displaying low specific capacity and poor cycling performance owing to the residual of a mass of soft-template (C12H27N) and intrinsic low conductivity of VOx. Cation exchange technique and oxidative polymerization process of pyrrole monomers were conducted to wipe off partial soft-template without electrochemical activity within VOxNTs and simultaneously form polypyrrole coating on VOxNTs, respectively. The resulting polypyrrole/VOxNTs nanocomposite delivers much improved capacity and cyclic stability. Further optimizations, such as complete elimination of organic template and enhancing the crystallinity, can make this unique nanostructure a promising cathode for LIBs.

Cycling Stability of a VOx Nanotube Cathode in Mixture of Ethyl Acetate and Tetramethylsilane-Based Electrolytes for Rechargeable Mg-Ion Batteries.

The electrochemical cycling performance of vanadium oxide nanotubes (VOx-NTs) for Mg-ion insertion/extraction was investigated in acetonitrile (AN) and tetramethylsilane (TMS)-ethyl acetate (EA) electrolytes with Mg(ClO4)2 salt. When cycled in TMS-EA solution, the VOx-NT exhibited a higher capacity retention than when cycled in AN solution. The significant degradation of capacity in AN solution resulted from increased charge-transfer resistance caused by the reaction products of the electrolyte during cycling. Mixed TMS-EA solvent systems can increase the cell performance and stability of Mg-electrolytes owing to the higher stability of TMS toward oxidation and the strong Mg-coordination ability of EA. These results indicate that the interfacial stability of the electrolyte during the charging process plays a crucial role in determining the capacity retention of VOx-NT for Mg insertion/extraction.

Transmission electron microscopy characterization of different nanotubes

ABSTRACTThe aim of this study is to present transmission electron microscopy (TEM) as a powerful instrument for characterization of nanostructural materials, in particular, nanotubes. Various nanotubes such as typical multiwall carbon nanotubes (MWCNTs), high-crystalline MWCNTs, and vanadium oxide nanotubes (VONTs) in different conditions are investigated by a TEM (Philips EM208S-100 kV). This work was carried out by analysis and investigation of TEM micrographs. In addition, the lattice structures of MWCNTs and VONTs were obtained by electron diffraction patterns (EDPs). The parameters of nanotubes such as length, diameter, number of walls, statistical distribution of diameter and atomic structures including lattice parameter information, and exact crystallographic description of crystal can be obtained by TEM. In fact, main crystallographic features and structural properties of nanotubes are determined and explained by means of EDP technique. Finally, this investigation will determine that characterization of nanotubes becomes easy by TEM and EDP techniques.

Electrochemical performances of nanostructured vanadium oxides

Vanadium oxide nanotubes (VOx-NTs) and nanourchin (4-phenylbutylamine/vanadium oxide) have been synthesized via one-step hydrothermal treatment. Compounds were analyzed through X-ray powder diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV curves illustrate reversible redox behavior with charge-discharge cycling corresponding to the reversible lithium intercalation/deintercalation. The EIS spectra were carried out in order to investigate the Li+ insertion mechanism at the electrode/electrolyte interface and evaluate the diffusion of Li+ within the bulk of cathode material.

Synthesis of nanostructured solid-state phases of V7O16 and V2O5 compounds for ppb-level detection of ammonia

Solid state phase of V7O16 with separate V2O5 phase were fabricated by pulsed laser deposition. The crystal structure and symmetry of the deposited films were studied with X-ray diffraction and Raman spectroscopy, respectively. Rietveld analysis was performed to the X-ray diffraction measurement results. The surface potentials and morphologies of the films were studied with atomic force microscopy, and microstructure of the thin films was analysed by transmission electron microscopy. Raman spectroscopy and Rietveld refinement results confirmed that the thin-film crystal structures varied between orthorombic V2O5 phase and another phase, triclinic V7O16, previously found only in the walls of vanadium oxide nanotubes (VOx-NT), bound together with organic amine. We have earlier presented the first results of stable and pure metal-oxide solid-state phase of V7O16 manufactured from ceramic V2O5 target. Here we show more detailed study of these structures. The microstructure studies showed a variation on the porosity of the films according to crystal structures and also some fibre-like nanostructures were found in the films. The surface morphology depended strongly on the crystal structure and the surface potential studies showed ∼50 meV difference in the work function values between the phases. Compounds were found to be extremely sensitive towards ammonia, NH3, down to ∼40 ppb concentrations, and have shown to have the stability and selectivity to control the Selective Catalytic Reduction process, where nitrogen oxides are reduced by ammonia in, e.g. diesel exhausts.

Optimizing the structure and yield of vanadium oxide nanotubes by periodic 2D layer scrolling

Structural uniformity of vanadium oxide nanotubes is possible by ensuring that 2D crystalline lamina maintain a defined thickness and interlayer spacing during scrolling. These parameters are sensitive to uniform packing of amine molecular templates.