A Simple and General Method for the Synthesis of Multicomponent Na2V6O16·3H2O Single-Crystal Nanobelts

Hewettite ZnV6 O16 ⋅ 8H2 O with Remarkably Stable Layers and Ultralarge Interlayer Spacing for High-Performance Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries (ZIBs) are promising candidates for grid-scale energy storage because of their intrinsic safety, low-cost and high energy-intensity. Vanadium-based materials are widely used as the cathode of ZIBs, especially A₂ V₆ O₁₆  ⋅ nH₂ O (AVO, A=NH₄ ⁺ , Na, K). However, AVO suffers from serious dissolution, phase transformation and narrow gallery spacing (∼3 Å), leading to poor cycling stability and rate capability. Herein, we unveiled the root cause of the performance degradation in the AVO cathode and therefore developed a new high-performance cathode of ZnV₆ O₁₆  ⋅ 8H₂ O (ZVO) for ZIB. Through a method of ion exchange induced phase transformation, AVO was converted to hewettite ZVO with larger gallery spacing (∼6 Å) and more stable V₆ O₁₆ layers. ZVO cathode thus constructed delivers a high capacity of 365 and 170 mAh g^-1 at 0.5 and 15 A g^-1 , while 86 % and 70 % of its capacity are retained at 0.5 A g^-1 after 300 cycles and at 15 A g^-1 after 10000 cycles, substantially better than conventional AVO.

Vanadium pentaoxide-doped waste plastic-derived graphene nanocomposite for supercapacitors: a comparative electrochemical study of low and high metal oxide doping

We report the bulk phase synthesis of graphene sheets using waste plastic (WP) as a precursor following a modified pyrolysis approach. Furthermore, the low and high mass loading of vanadium pentaoxide was performed on graphene sheets in 1 : 10 and 1 : 1 ratios, respectively. Advanced characterization techniques such as Raman spectroscopy, FT-IR spectroscopy, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA) analysis, and SEM imaging were used to confirm the synthesis of graphene. FT-IR spectroscopy confirmed that the resonating structure affects the bond strength in the composite, which enables peak shifting in the FT-IR spectrum of the composite. Furthermore, bandgap analysis has been performed using UV-Vis spectroscopy, which confirmed the synthesis of the composites. The developed vanadium-doped graphene was used as the active material for the fabrication of supercapacitor electrodes. The electrochemical performance of these devices was evaluated in 1 M H3PO4 solution using cyclic voltammetry (CV), galvanic charge-discharge (GCD) analysis, and electrochemical impedance spectroscopy (EIS). Fabricated cells 1 and 2 showed exceptional specific capacitances of 139.7 F g-1 and 51.2 F g-1 at 5 mV s-1 scan rate, respectively. Cell 1 showed a huge power density of 5312 W kg-1 and an energy density of 19.7 W h kg-1. Conversely, cell 2 showed a comparatively lower power density of 1941 W kg-1 and an energy density of 7.2 W h kg-1 at a 5 mV s-1 scan rate. Moreover, we disclose some brief conclusions on the performance, mechanism, and required modifications that can improve the performance of such devices. This approach can surely help with universal WP problems as well as the development of high-performance supercapacitors.

Vanadium-based nanowires for sodium-ion batteries

Sodium-ion batteries (SIBs) have received great attention because of the abundance source and low cost. To date, some Na⁺ storage materials have achieved great performance, but the larger Na⁺ radius and more complex Na⁺ storage mechanism compared with Li⁺ still limit the energy density and power density. This review systematically summarizes emerging synthetic technologies of vanadium-based materials from simple nanowires to complicated modified/optimized structures. In addition, vanadium-based nanowire materials are reviewed at both the cathode and anode side, and advantages and drawbacks are proposed to explain the challenges facing application of novel materials. Furthermore, a vanadium-based single-nanowire device is reported to reveal the Na⁺ storage mechanism, which contributes to the understanding of the reaction in SIBs. Finally, this review summarizes the current development challenges of SIBs and looks forward to the future development prospects of vanadium-based nanowires, providing a new direction for further applications of SIBs.

Facile synthesis of ultrathin Ni-MOF nanobelts for high-efficiency determination of glucose in human serum

Ultrathin Ni-MOF nanobelts, [Ni₂₀(C₅H₆O₄)₂₀(H₂O)₈]·40H₂O(Ni-MIL-77 NBs), were synthesized by a facile one-pot solution process and can be used as an efficient catalyst electrode for glucose oxidation under alkaline conditions. Electrochemical measurements demonstrate that the NB/GCE, when used as a non-enzymatic glucose sensor, offers superior analytical performances with a wide linear range (from 1 μM to 500 μM), a low detection limit (0.25 μM, signal-to-noise = 3), and a response sensitivity of 1.542 μA mM^-1 cm^-2. Moreover, it can also be applied for glucose detection in human blood serum with the relative standard deviation (RSD) of 7.41%, showing the high precision of the sensor in measuring real samples.

Ultra-long Na2V6O16·xH2O nanowires: large-scale synthesis and application in binder-free flexible cathodes for lithium ion batteries

Large-scale synthesis and application of ultra-long Na₂V₆O₁₆·xH₂O nanowires as binder-free flexible cathodes for high performance LIBs are demonstrated.

Pure Single-Crystalline Na1.1V3O7.9 Nanobelts as Superior Cathode Materials for Rechargeable Sodium-Ion Batteries

Pure single-crystalline Na1.1V3O7.9 nanobelts are successfully synthesized for the first time via a facile yet effective strategy. When used as cathode materials for Na-ion batteries, the novel nanobelts exhibit excellent electrochemical performance. Given the ease and effectiveness of the synthesis route as well as the very promising electrochemical performance, the results obtained may be extended to other next-generation cathode materials for Na-ion batteries.

Large-scale growth of hierarchical transition-metal vanadate nanosheets on metal meshes as monolith catalysts for De-NO(x) reaction

A facile method is developed for the large-scale growth of hierarchical transition-metal (Cu, Fe, and Ni) vanadate nanosheets on corresponding metal mesh as supports. The hierarchical transition-metal vanadate nanosheets were in situ grown on the metal meshes through an orientational etching process and simultaneous nucleation and growth process. Interestingly, the morphologies of the vanadate nanosheets are governed by the balance between dissolution rate and nucleation rate. Thus, the sizes and the thicknesses of the nanosheets could be facilely controlled by the reaction duration, the acidity of the solution and the concentration of vanadate precursor. Furthermore, the hierarchical transition-metal vanadate nanosheets supported on metal meshes are used as monolith catalysts for the selective catalytic reduction (SCR) of NO with NH3. The iron mesh based monolith catalyst shows excellent de-NOx performance with high efficiency and stability in the presence of SO2 and H2O, which provide a promising monolith de-NOx catalyst for stationary source at medium temperatures.

One-step hydrothermal synthesis of graphene decorated V2O5 nanobelts for enhanced electrochemical energy storage

Graphene-decorated V2O5 nanobelts (GVNBs) were synthesized via a low-temperature hydrothermal method in a single step. V2O5 nanobelts (VNBs) were formed in the presence of graphene oxide, a mild oxidant, which also enhanced the conductivity of GVNBs. From the electron energy loss spectroscopy analysis, the reduced graphene oxide (rGO) are inserted into the layered crystal structure of V2O5 nanobelts, which further confirmed the enhanced conductivity of the nanobelts. The electrochemical energy-storage capacity of GVNBs was investigated for supercapacitor applications. The specific capacitance of GVNBs was evaluated using cyclic voltammetry (CV) and charge/discharge (CD) studies. The GVNBs having V2O5-rich composite, namely, V3G1 (VO/GO = 3:1), showed superior specific capacitance in comparison to the other composites (V1G1 and V1G3) and the pure materials. Moreover, the V3G1 composite showed excellent cyclic stability and the capacitance retention of about 82% was observed even after 5000 cycles.

Rational design of one-dimensional vanadium(v) oxide nanocrystals: an insight into the physico-chemical parameters controlling the crystal structure, morphology and size of particles

This highlight deals with the recent advances on the synthesis in aqueous solution of one-dimensional vanadium(v) oxide nanocrystals.

Controllable synthesis and morphology evolution from two-dimensions to one-dimension of layered K2V6O16·nH2O

In a hydrothermal process, layered K₂V₆O₁₆·2.7H₂O platelike crystals are split into layered K₂V₆O₁₆·1.5H₂O fiberlike crystals.

Hydrothermal growth and characterization of length tunable porous iron vanadate one-dimensional nanostructures

The length of porous FeV_xO_y1-D nanostructures could be tuned from several micrometers to several millimeters.

Na₂V₆O₁₆·xH₂O nanoribbons: large-scale synthesis and visible-light photocatalytic activity of CO₂ into solar fuels

An ultra-thin and super-long Na₂V₆O₁₆·xH₂O nanoribbon of ∼5 nm thickness and ∼500 μm length was synthesized by a hydrothermal method, using a freshly prepared V(3+) species precursor solution by directly dissolving a vanadium metal thread in a NaNO₃ solution using a solid-liquid phase arc discharge (SLPAD) technique. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques were used to characterize the structure, morphology, and chemical composition. The super-long and ultra-thin geometry of the Na₂V₆O₁₆·xH₂O nanoribbons is proven to greatly promote the photocatalytic activity toward reduction of CO₂ into renewable hydrocarbon fuel (CH₄) in the presence of water vapor under visible-light irradiation.

Crystalline Li3V6O16 rods as high-capacity anode materials for aqueous rechargeable lithium batteries (ARLB)

Crystalline Li₃V₆O₁₆ rods were prepared and used as anode materials for aqueous rechargeable lithium ion batteries (ARLBs).

Synthesis of Na(1.25)V(3)O(8) nanobelts with excellent long-term stability for rechargeable lithium-ion batteries

Sodium vanadium oxide (Na1.25V3O8) nanobelts have been successfully prepared by a facile sol-gel route with subsequent calcination. The morphologies and the crystallinity of the as-prepared Na1.25V3O8 nanobelts can be easily controlled by the calcination temperatures. As cathode materials for lithium ion batteries, the Na1.25V3O8 nanobelts synthesized at 400 °C exhibit a relatively high specific discharge capacity of 225 mA h g(-1) and excellent stability at 100 mA g(-1). The nanobelt-structured electrode can retain 94% of the initial capacity even after 450 cycles at the current density of 200 mA g(-1). The good electrochemical performance is attributed to their nanosized thickness and good crystallinity. The superior electrochemical performance demonstrates the Na1.25V3O8 nanobelts are promising cathode materials for secondary lithium batteries.

Effects of calcination temperature on microstructures and photocatalytic activity of titanate nanotube films prepared by an EPD method

Titanate nanotube films are fabricated on F-doped SnO(2)-coated glass substrates via an electrophoretic deposition method using hydrothermally prepared titanate nanotubes as precursors. The effects of calcination temperature on the microstructures and photoactivity of as-prepared titanate nanotube films are investigated and discussed. The results indicate that the intercalated sodium ions (Na(+)) in the as-prepared titanate nanotubes are easily removed during the electrophoretic deposition. The phase transformation of titanate to anatase and diffusion of Na(+) ions from glass substrates into films occur at 400 °C. With increasing calcination temperature, the crystallization of anatase enhances and sodium content in the films increases. At 500 °C, the tubular structure still holds and the films show the highest photocatalytic activity probably due to their good crystallization, large specific surface areas and tubular structures.

Synthesis and field emission of single-crystalline copper vanadate nanobelts

Single-crystalline nanobelts of a nonstoichiometric compound Cu(1.55)V(2)O(6.55), with a thickness of 40-60 nm, width of 50-300 nm and length of several micrometers, have been synthesized on a large scale by a hydrothermal method. The structures and morphologies of the nanobelts were characterized by x-ray powder diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. A probable growth mechanism has also been discussed. The nanobelts exhibit a turn-on field of 11.0 V µm(-1), which is defined as the macroscopic field required to produce a current density of 10 µA cm(-2). It is anticipated that the nanobelts can serve as a candidate material for future field emitters.

From Multicomponent precursor to nanoparticle nanoribbons of ZnO

A simple mild solution method is developed to synthesize a novel nanoribbon multicomponent precursor. A new 1-D nanostructure, porous structured nanoribbons which are self-assembled by textured ZnO nanoparticles, was found upon removal of ligand molecules from the ribbonlike precursor. The structure combines 1-dimensional geometry with nanoparticle morphology and displays porous structure because there are gaps/pores between the particles. The orientation textured structure of the ZnO nanoparticles can be formed by controlling the annealing time. The ZnO nanoparticle nanoribbons exhibit a long geometrical shape, uniformity, a high aspect ratio, and different optical activities with different nanostuctures. These findings demonstrate a convenient, simple technique for production of the novel one-dimensional semiconductor nanostructure suitable for subsequent processing into nanostructures, materials, and devices.

Photocatalytic activity of the calcined H-titanate nanowires for photocatalytic oxidation of acetone in air

Hydrogen titanate (H-titanate) nanowires were prepared via a hydrothermal reaction of TiO2 powders (P25) in KOH solutions and then calcined at various temperatures. The phase structure, crystallite size, morphology, specific surface area, and pore structures of the calcined H-titanate nanowires at various temperatures were characterized with field emission scanning electron microscope, X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption isotherms, and their photocatalytic activities were evaluated by photocatalytic oxidation of acetone in air. With increasing calcination temperature, the specific surface area and porosity of the calcined samples steadily decreased. At a calcination temperature range of 400-600 degrees C, the calcined H-titanate nanowires showed higher photocatalytic activity than P25 powders for photocatalytic oxidation of acetone. Especially, at 500 degrees C, the calcined H-titanate nanowires showed the highest photocatalytic activity, which exceeded that of P25 by a factor of about 1.8 times. This can be attributed to the synergetic effect of larger specific surface area, higher pore volume and the presence of brookite TiO2. With further increase in the calcination temperature (700-900 degrees C), the photocatalytic activity of the samples decreased obviously owing to the growth of TiO2 crystallites.