V2O5 Particles Research Articles

Pt-like hydrogen evolution on a V2O5/Ni(OH)2 electrocatalyst

We report a highly efficient and cost-effective binder-free catalyst for the hydrogen evolution reaction (HER) using V2O5 particles on nickel foam (NF) (V2O5/Ni(OH)2@NF).

On the compactness of the oxide layer induced by utilizing a porosification agent

It is imperative to control the pore density and distribution of pores produced inevitably on the surface of the oxide layer produced by plasma electrolysis (PE) process since these factors could affect the final electrochemical performance of these layers. Up to this study, utilizing a porosification agent in order to optimize the compactness of the oxide layer grown on Al alloy via PE has been rarely reported. Here, a simple novel strategy was proposed in the present work to control these defects by triggering the incorporation of V2O5 through utilizing a high concentration of phosphate ions which was reported extensively as a porosification agent during PE process. For this aim, Al-Mg-Si alloy samples were treated by PE under AC conditions at a current density of 75 mA/cm2 for 5 min from V2O5-based electrolytes with 0, 6 and 18 g/L of Na3PO4. It was found that the oxide layer made from electrolyte with 18 g/L Na3PO4 was less porous and smoother than the counterparts with 0 and 6 g/L Na3PO4. This result was attributed to the development of uniform fine plasma sparks at the high concentration of Na3PO4 responsible for facilitating the incorporation of V2O5 particles into the oxide layer which resulted eventually in the formation of a conformal black coating. Accordingly, the electrochemical response of the oxide layer with 18 g/L Na3PO4 was superior to that with 6 g/L Na3PO4. This study would potentially pave a way to obtain a fully compact oxide layer with controllable surface properties in optical and aerospace applications.

Fabrication of pure V2O3 powders by reducing V2O5 powders with CO-CO2 mixed gases

Vanadium (III) oxide (V2O3) can be widely used in the fields of metal ceramics, catalysts, temperature sensors, and cathode materials. In this paper, V2O3 powders are prepared via a gas-based reduction by the mixed gases of CO and CO2 in the temperature range of 783–963 K. The effects of the CO percentage and reaction temperature on the phase transition and morphology evolution of the final products are investigated. The results reveal that the reduction mechanism are different at low and high temperatures. At a temperature lower than the melting point of V2O5 (943 K), the phase transformation sequence can be described as follows: V2O5→V6O13→VO2→V2O3. The reduction process is dominated by a pseudomorphic transformation mechanism, under which the morphology of the produced V2O3 particles roughly keeps the original morphology of V2O5 particles. As the temperature is higher than the melting point of V2O5, the reduction process becomes a gas-liquid reaction, and the reaction rate obviously decreases. Compared with the V2O3 prepared at low temperatures, the morphology becomes much more irregular and compact. It is also found from the experiments that the introduction of CO2 can restrain the carbon deposition reaction and assist in increasing the purity of the V2O3 powders.

Peapod-like CNT@V2O3 with Superior Electrochemical Performance as an Anode for Lithium-Ion Batteries

Peapod-like CNT@V2O3 (CNT = carbon nanotube) with small V2O3 nanoparticles (13 nm) and a good electronic conductive network (the CNTs) was constructed through a reflux and annealing process. As anode materials, CNT@V2O3 shows admirable capacity (652.4 mA h g–1 at 500 mA g–1 for 200 cycles), a long lifespan, and good rate performance. Compared with V2O3, the peapod-like CNT@V2O3 composites have superior electrochemical performance due to the porous structure, the V2O3 particles, and peapod-like architecture, which reduce the transmission distance of lithium ion, enlarge the superficial area, and enhance structural stability. As a result, the unique composite material with a peapod-like structure is an ideal anode material.

A facile pathway to prepare VO2 and V2O3 powders via a carbothermal reduction process

The development of a highly efficient and low cost production process is instrumental for the wide application of VO2 and V2O3. In this paper, VO2 and V2O3 powders are successfully prepared via carbothermal reduction of V2O5 in a flowing Ar atmosphere at 973 K and 1423 K, respectively. Compared with the traditional methods, graphite is used as a reductant, which resulted in a low cost. The experimental results show that a high temperature assists in improving the kinetic rate. The phase transformation during the low-temperature reduction process between 948 K and 973 K occurs in the following sequential order: V2O5→V6O13→VO2. When the temperature is 1423 K or 1473 K, the phase transformation can be described as follows: V2O5→V3O5→V2O3. Owing to the shrink of the volume, the as-prepared VO2 and V2O3 particles could not maintain the original micro-morphology of V2O5. Relative to VO2, the as-prepared V2O3 particles are porous. It is also concluded that the V2O3 can be easily oxidized to VO2, when the partial pressure of O2 is in the range of 10−8 atm to 10−1 atm. Therefore, a reasonable reaction temperature and reaction time are important to prepare high purity V2O3.

Effect of V2O5 particles size on oxidation of m-xylene: Vapor-phase oxidation of m-xylene by using V2O5 encapsulated into the TiO2 lattice as an efficient and reusable catalyst

The selectivity and over-oxidation obtained in the oxidation of m-xylene to isophthalic acid by V2O5 nanoparticles encapsulated in TiO2 matrix are controlled by the size of the V2O5 nanoparticles. In this reaction when the size of V2O5 nanoparticles was less than 45 nm at least 16–30% of the m-xylene was lost as carbon oxides. In this work, V2O5@TiO2 catalysts, with V2O5 loadings from 10 to 20 wt% were prepared by trapping V2O5 nanoparticles in a matrix of mesoporous TiO2. We demonstrate herein results of m-xylene oxidation in a fixed-bed reactor (i.d. = 10 mm) for production of isophthalic acid. The air-calcined samples of the catalysts were characterized by different techniques such as FT-IR, XRD, Diffuse-reflectance UV–Vis, FE-SEM, EDX, BET, XPS, and TEM. This novel configuration of V2O5 particles in the TiO2 matrix not only prevents leaching of the catalyst but also improves the catalyst reusability. The optimal amount of V2O5 trapped in the TiO2 matrix was 15 wt%. The best V2O5@TiO2 catalyst activation temperature was 350 °C.

Evaluation of TiO2/V2O5 and N,F-doped-TiO2/V2O5 nanocomposite photocatalysts toward reduction of Cr(VI) and oxidation reactions by [rad]OH radicals

V2O5/TiO2 photocatalysts, with V2O5 particles supported on TiO2 (TV), N-TiO2 (NTV) and N/F-TiO2 (NFTV), were prepared with 5%wt. V2O5 loading and 450, 550°C as calcination temperatures. XRD analysis showed the formation of anatase TiO2 and very small peaks of V2O5. DRS UV–vis spectra showed that V2O5 coupling extended the absorption edge into the visible light region. Photocatalysts calcined at 450°C exhibited higher rates of Cr(VI) reduction and OH radical photogeneration than photocatalysts calcined at 550°C. For catalysts at 450°C, photocatalytic reduction of Cr(VI) follows the trend ΤV450>ΝΤV450>ΝFTV450 while the OH generation followed the reverse trend.

A Mechanistic Understanding of Hydrogen Peroxide Decomposition by Vanadium Minerals for Diethyl Phthalate Degradation.

The interaction of naturally occurring minerals with H2O2 affects the remediation efficiency of polluted sites in in situ chemical oxidation (ISCO) treatments. However, interactions between vanadium(V) minerals and H2O2 have rarely been explored. In this study, H2O2 decomposition by various vanadium-containing minerals including V(III), V(IV), and V(V) oxides was examined, and the mechanism of hydroxyl radical (•OH) generation for contaminant degradation was studied. Vanadium minerals were found to catalyze H2O2 decomposition efficiently to produce •OH for diethyl phthalate (DEP) degradation in both aqueous solutions with a wide pH range and in soil slurry. Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) analyses, and free radical quenching studies suggested that •OH was produced via single electron transfer from V(III)/V(IV) to H2O2 followed a Fenton-like pathway on the surface of V2O3 and VO2 particles, whereas the oxygen vacancy (OV) was mainly responsible for •OH formation on the surface of V2O5 particles. This study provides new insight into the mechanism of interactions between vanadium minerals and H2O2 during H2O2-based ISCO.

Designed Synthesis and Supercapacitor Electrode of V2O3@C Core‐shell Structured Nanorods with Excellent Pseudo‐capacitance in Na2SO4 Neutral Electrolyte

AbstractV2O3@C core‐shell structured nanorods (VCNR) were successfully prepared using V2O5 nanowires and glucose via a facile hydrothermal route combination of calcination. VCNR comprised of core‐shell structures with V2O3 cores and amorphous carbon shells. Electrochemical properties of VCNR as supercapacitor electrodes were studied in Na2SO4 neutral electrolyte. Results demonstrated that VCNR featured capacitive behavior originating from pseudocapacitance. Specific capacitances of VCNR at 0.5, 1, 2, 5 and 10 A⋅g−1 were achieved to 219, 192, 148, 127 and 119 F⋅g−1, respectively, and VCNR displayed higher specific capacitance than the values of carbon spheres and V2O3 particles. Maximum specific capacitance of VCNR reached 219 F⋅g−1 at 0.5 A⋅g−1 in present study, which was superior to the reported values of V2O3‐based materials and VO2‐based materials. Capacitance retention of VCNR was 100% after 700 cycles and 66% after 1000 cycles. Findings in present study proved that VCNR could be promising candidate as an ideal material for supercapacitors’ electrode.

Structure property correlation of electro-codeposited Cu-Al-V2O5 composite coating obtained from Al-V2O5 dispersed electrolyte

The present work depicts electro-codeposition of copper along with Al (size ~ 20 nm) and V2O5 (size ~ 350 nm) particles as second phase reinforcements on copper substrate. Different compositions of Cu-Al-V2O5 composite coatings were formed from acidic electrolyte with addition of 5 g/l Al and 10 g/l V2O5 particles in the deposition bath with 8 A/dm2 current density both in the presence and absence of CTAB. Field emission scanning electron microscope (FESEM) image of non-CTAB added coatings show coarser structure compared to CTAB added coatings. Mechanical characterizations of the coatings portray better hardness and wear resistance of composite coatings compared to unreinforced Cu coated sample. Among the non-CTAB and CTAB assisted coatings, CTAB treated specimens have better mechanical properties in terms of hardness and wear resistance compared to non-CTAB ones due to finer coating matrix and formation of (220) texture. The downgrading of electrical conductivity values of the composite coatings was due to the codeposition of insulating V2O5 and finer coating matrix. Aluminum in the coating tends to maintain the electrical conductivity but provides little strengthening effect.

Efficient charge carrier separation and enhanced UV–visible photocatalytic activity in macroporous TiO2 decorated with V2O5/Ag nanostructures

We report a novel structure – macroporous TiO2 decorated with V2O5/Ag nanoparticles – for enhanced visible photocatalytic activity by efficient charge carrier separation and enhanced visible light absorption. They are found to be much superior to TiO2∕V2O5, TiO2/Ag and V2O5/Ag composite particles. V2O5 particles are found to reduce the recombination of photogenerated carriers from TiO2 under UV exposure by charge transfer mechanism along with the increased absorption in the visible region. Further decoration with Ag nanoparticles enables efficient absorption of light over the visible region due to the localized surface plasmon resonance. In addition, Ag nanoparticles act as effective electron traps for the photogenerated electrons from V2O5 and enhances the photocatalytic activity in the visible region. Rate constant values obtained for TiO2∕V2O5 and TiO2∕V2O5/Ag heterostructures are 0.009 and 0.014 min−1 respectively. Heterostructures are also found to be recyclable in nature making them highly suitable for visible photocatalytic applications.

Polypyrrole–vanadium oxide nanocomposite: polymer dominates crystallanity and oxide dominates conductivity

A hybrid nanocomposite of polypyrrole (Ppy)–V2O5 has been fabricated and characterized for better understanding of material enabling one to use this for appropriate application as the nanocomposite shows better thermal stability. The characterization has been done using XRD, FT-IR, FESEM, and UV–Vis for their structure, surface morphology, respectively, along with TGA and two-probe method used for checking thermal stability, and DC electrical conductance and dielectric behavior of the electrical phenomena of sample. The analysis of XRD demonstrates that crystallinity of nanocomposites is the same as that of the polymer, even though interaction between conducting Ppy and V2O5 is present as evident from FT-IR spectroscopy. A variation in bandgap, in comparison with Ppy, is observed when V2O5 is added into it. The microstructural study of nanocomposites shows encapsulation of V2O5 particles in Ppy matrix with changes in morphology with increase in doping. Conductance results show that electrical conductivity of Ppy decayed on adding V2O5. It has also been found that addition of V2O5 in Ppy has noticeable effect on the dielectric properties.

Photocatalytic Water Splitting for O₂ Production under Visible Light Irradiation Using NdVO₄-V₂O₅ Hybrid Powders.

The study investigated photocatalytic water splitting for O2 production under visible light irradiation using neodymium vanadium oxide (NdVO4) and vanadium oxide (V2O5) hybrid powders. The results in a sacrificial agent of 0.01 M AgNO3 solution were obtained, and the highest photocatalytic O2 evolution was 2.63 μmol/h, when the hybrid powders were prepared by mixing Nd and V at a volume ratio of 1:3 at a calcination temperature of 350 °C for 1 h. The hybrid powders were synthesized by neodymium nitrate and ammonium metavanadate using the glycothermal method in ethylene glycol at 120 °C for 1 h. The hybrid powders consisted of two shapes, NdVO4 nanoparticles and the cylindrical V2O5 particles, and they possessed the ability for photocatalytic oxygen (O2) evolution during irradiation with visible light. The band gaps and structures of the hybrid powders were analyzed using UV-visible spectroscopy and transmission electron microscopy.

Electrochemical Performance of a V2O5 Cathode for a Sodium Ion Battery

In this paper, layered vanadium pentoxide (V2O5) is employed as a cathode material for a sodium ion battery. The V2O5 particle sizes range from 200 nm to 500 nm and the shapes of the aggregated V2O5 particles are non-homogeneous and irregular. The material exhibits a first discharge capacity of approximately 208.1 mAh g−1. The structure of V2O5 changes to a NaxV2O5 structure after Na+ insertion at the first discharge; the structure of NaxV2O5 remains stable␣during cycling. After 40 cycles, the discharge capacity retains 61.2% of the capacity of the second cycle. The capacity of V2O5 at a high charge/discharge current rate of 1.0 C is 49.1% of capacity at 0.1 C. Furthermore, the capacity returns to the initial value as the discharge rate returns to 0.1 C. The results of electrochemical performance tests indicate that V2O5 is a potential cathode material for sodium ion batteries.

Synthesis of amorphous carbon coated on V2O3 core-shell composites for enhancing the electrochemical properties of V2O3 as supercapacitor electrode

V2O3@C core-shell composites were successfully synthesized by the heat treatment with H2V3O8@C core-shell composites. The composition and phase of the samples were evaluated by X-ray powder diffraction, energy-dispersive X-ray spectrometer, X-ray photoelectron spectroscopy, elemental analysis, infrared spectroscopy and Raman spectroscopy. The morphology and structure of the samples were observed by the means of scanning electron microscopy and transmission electron microscopy. The results revealed that the samples consisted of the crystal V2O3 phase and the amorphous carbon phase, and their morphology were well-defined core-shell nanobelts, and each V2O3 core was encapsulated into amorphous carbon. The Brunauer-Emmet-Teller result showed that V2O3@C core-shell composites displayed the specific surface area as high as 83.2m2g−1. Furthermore, the electrochemical properties of V2O3@C core-shell composites as supercapacitor electrode were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. For comparison, the synthesis and electrochemical properties of carbon spheres and V2O3 particles were also investigated. The results showed the measured capacitance of V2O3@C core-shell composites was based on the pseudocapacitance. V2O3@C core-shell composites displayed the highest specific capacitance and electric conductivity among carbon spheres, V2O3 particles and V2O3@C core-shell composites. The specific capacitances were 223, 180, 146, 112, 92 and 72 Fg−1 at the discharge current densities of 0.1, 0.5, 1, 2, 5 and 10 Ag−1, respectively. The present work provided a strategy to prepare core-shell structured composites of metal oxides with improved electrochemical performance for supercapacitor electrodes.

Carbon Nanotube Modified V2O5 Porous Microspheres as Cathodes for High‐Performance Lithium‐Ion Batteries

AbstractFor the first time, V2O5/carbon nanotube (CNT) porous microspheres (VCMs) constructed from V2O5 particles homogenously wrapped in highly conductive CNTs have been synthesized through a facile spray‐drying route by using commercial V2O5 and CNTs as starting materials. Compared with bare commercial V2O5 particles, the electrochemical performance of VCM is significantly enhanced: it exhibits a large specific capacity of 242.3 mAh g−1, which is about 69 % higher than that of bare commercial V2O5 (145.4 mAh g−1); the capacity remains 223.8 mAh g−1 at 0.2 C (1 C=294 mAh g−1) after 80 cycles with a high capacity retention of 92.3 %. The C‐rate capacities at 1, 2, 5, and 10 C are 180.8, 154.1, 134.8, and 109.3 mAh g−1, respectively; these values indicate excellent rate performance. The remarkable performance enhancement is attributed to the interconnected network of conductive CNTs, which guarantees high conductivity and enables fast electron transport between CNTs and V2O5 of the uniformly dispersed VCM. Moreover, VCM provides a hierarchical template to accommodate the structural degradation and delamination of V2O5 particles during electrochemical cycling. The proposed spray‐drying strategy is facile, effective, and easy to realize on a large scale for the low‐cost industrial production of V2O5/CNT composite cathodes, which can be extended to produce other high‐capacity electrode materials with large volume variations and low electrical conductivities.

Mercury oxidation during coal combustion by injection of vanadium pentoxide (V2O5)

Although there are many commercially available methods to capture Hg emission from coal combustion, it is still difficult to use a single method that can control Hg emission both efficiently and economically from coal combustors due to the varying coal seams, operating conditions and downstream control devices. One methodology is the use of sorbent injection at elevated temperatures; and is examined in this study. V2O5 was tested as the sorbent and was found to effectively oxidize elemental mercury (Hg0). Ultrafine V2O5 particles are formed during the combustion process resulting in a high surface area aerosol that can effectively catalyze the oxidation of Hg0. The effect of varying chlorine (Cl) concentration in coal on Hg0 oxidation was also examined. The result shows that Cl can enhance Hg0 oxidation on the V2O5 surface.

A comparative assessment of the acute inhalation toxicity of vanadium compounds

Vanadium compounds have become important in industrial processes, resulting in workplace exposure potential and are present in ambient air as a result of fossil fuel combustion. A series of acute nose-only inhalation toxicity studies was conducted in both rats and mice in order to obtain comparative data on the acute toxicity potential of compounds used commercially. V2O3, V2O4, and V2O5, which have different oxidation states (+3, +4, +5, respectively), were delivered as micronized powders; the highly water-soluble and hygroscopic VOSO4 (+4) could not be micronized and was instead delivered as a liquid aerosol from an aqueous solution. V2O5 was the most acutely toxic micronized powder in both species. Despite its lower overall percentage vanadium content, a liquid aerosol of VOSO4 was more toxic than the V2O5 particles in mice, but not in rats. These data suggest that an interaction of characteristics, i.e., bioavailability, solubility and oxidation state, as well as species sensitivity, likely affect the toxicity potential of vanadium compounds. Based on clinical observations and gross necropsy findings, the lung appeared to be the target organ for all compounds. The level of hazard posed will depend on the specific chemical form of the vanadium. Future work to define the inhalation toxicity potential of vanadium compounds of various oxidation states after repeated exposures will be important in understanding how the physico-chemical and biological characteristics of specific vanadium compounds interact to affect toxicity potential and the potential risks posed to human health.

μ2-Oxido bridged dinuclear vanadium(V) complex: Synthesis and characterization

μ2-Oxido bridged dinuclear vanadium(V) Schiff base complex with the general formula [VO2(L)]2·2CH3OH was synthesized and characterized. The X-ray results show the complex is dinuclear with two μ-O bridging ions, and the vanadium centers have an octahedral N2O4 coordination sphere. The tridentate Schiff base ligand L coordinated to vanadium(V) center as a monoanion in the basal plane. The basal plane is completed by one of the μ-O bridges. The other μ-O bridge coordinated to vanadium(V) center as apical direction. The two oxido bridged connected the two Vv centers together with the Vv-O-Vv angle of 101.21(6)°, the VO distances of 1.70(6) and 2.31(7) Å and the V⋯V separation of 3.113(5) Å. Finally, the complex was calcinated at 600 °C for 3 h. The FT-IR spectrum of the product shows the formation of the V2O5 particles.

Activation of persulfate with vanadium species for PCBs degradation: A mechanistic study

In the present study, the activation of persulfate (PS) with vanadium (V) species for PCBs (2,4,4′-trichlorobiphenyl [PCB28]) degradation was investigated for the first time. It was found that V2O3 exhibited high catalytic activity toward PS decomposition for PCB28 degradation. Even under near neutral pH (7.4), PCB28 was efficiently degraded in V2O3/PS. Sulfate radical anions (SO4−) and hydroxyl radicals (OH) were produced from PS activation with V2O3 for PCB28 degradation, and were characterized with electron paramagnetic resonance (EPR) technique. Free radical quenching studies showed that ethanol inhibited PCB28 degradation, while tert-butyl alcohol enhanced PCB28 degradation via reductive dechlorination with alcohol radicals. The pathway of PCB28 degradation was proposed on the basis of GC–MS analysis of intermediates of PCB28 degradation in V2O3/PS. The mechanisms of PS activation are elucidated. It was found that V(III) in V2O3 activated PS to form SO4− and V(IV) (VO2) via electron transfer process, and the formed V(IV) further transferred an electron to PS to generate SO4− and V(V) (V6O13), which were supported with XRD analysis. Furthermore, both VO2 and V2O5 can activate PS for PCB28 degradation, indicating that V(IV) would be regenerated from the reduction of V(V) by persulfate ions (S2O82−) on the surface of V2O5 particles. These findings would help to better understand the interactions between naturally occurring V minerals and PS, and provide a novel activator for PS activation to degrade contaminants.