Introduction Of Vanadium Research Articles

Electronic structure and delithiation mechanism of vanadium and nickel doped Li2MnPO4F cathode material for lithium-ion batteries

This study calculates the energy band structure and density of states of Lithium manganese fluorophosphate (Li2MnPO4F, a lithium transition metal phosphate compounds) using the first-principles plane-wave pseudopotential approach within the density-functional theory. The model of Li2M0.5Mn0.5PO4F (M = V, Ni) with transition metal doped Mn sites is constructed by using the CASTEP module. The calculation findings indicate that the transition metal doping can regulate the energy band structure of the intrinsic system, and Li2MnPO4F makes the band gap decrease, and the volume increase with the Li ions of being deintercalated, and the electrons can be readily stimulated from the valence band to the conduction band. The findings indicate that Li2MnPO4F is a favorable cathode material for high-voltage lithium ion batteries (LIBs). The introduction of vanadium (V) and nickel (Ni) doping reduces the band gap, facilitating an easier excitation of electrons from the valence band to the conduction band. This study provides a theoretical study of new cathode materials for high performance LIBs.

An iron-containing POM-based hybrid compound as a heterogeneous catalyst for one-step hydroxylation of benzene to phenol.

It is a major challenge to perform one-pot hydroxylation of benzene to phenol under mild conditions, which replaces the environmentally harmful cumene method. Thus, finding highly efficient heterogeneous catalysts that can be recycled is extremely significant. Herein, a (POM)-based hybrid compound {[FeII(pyim)2(C2H5O)][FeII(pyim)2(H2O)][PMoV2MoVI9VIV3O42]}·H2O (pyim = 2-(2-pyridyl)benzimidazole) (Fe2-PMo11V3) was successfully prepared by hydrothermal synthesis using typical Keggin POMs, iron ions and pyim ligands. Single-crystal diffraction shows that the Fe-pyim unit in Fe2-PMo11V3 forms a stable double-supported skeleton by Fe-O bonding to the polyacid anion. Remarkably, due to the introduction of vanadium, Fe2-PMo11V3 forms a divanadium-capped conformation. Benzene oxidation experiments indicated that Fe2-PMo11V3 can catalyze the benzene hydroxylation reaction to phenol in a mixed solution of acetonitrile and acetic acid containing H2O2 at 60 °C, affording a phenol yield of about 16.2% and a selectivity of about 94%.

Synthesis of malonic acid-VTiO2 photocatalysts for the photodegradation of micropollutant

Herein, a novel malonic acid-vanadium doped TiO2 (m-VTiO2) photocatalysts with different V ratios were synthesized via crosslinking and hydrothermal treatment. Malonic acid was employed as the cross-linking agent to chemically bind TiO2 and vanadium via its dicarboxylic functional group. The synthesized m-VTiO2 photocatalyst presents a large surface area with sheet-like morphology. XPS results revealed the existence of vanadium in the V5+ and V4+ states, and the binding energies of Ti-O bonds were changed significantly with the introduction of vanadium. The photocatalytic activity increased gradually with the vanadium content and decreased when it attained the maximum value at 7.5% m-VTiO2 for sulfamethoxazole (SMX). The optimal photocatalyst (m-TV3) presents the best photocatalytic activity for SMX owing to its improved surface area. The reaction rate of 7.5 % m-VTiO2 was 4.86-fold higher than that of the un-doped TiO2 particle under visible irradiation. The photodegradation efficiency of SMX was still up to 86.07 % after six cycling runs, indicating the good reusability of the photocatalyst. More importantly, the photocatalysts also show high photocatalytic activity for RHB dye. In addition, a potential mechanism for enhancing the photocatalytic activity under visible irradiation was put forth.

Study on effect of vanadium doping in cesium tungsten bronze system and application in HER

Increasing demand for energy and the crisis of fossil fuels have led researchers to search for an alternative energy source. Hydrogen is the cleanest energy source producing water as fuel cells exhaust. However, producing hydrogen could be crucial as only some active catalysts produce pure hydrogen. The expense due to the scarcity of the state-of-the-art catalyst (platinum) for the Hydrogen Evolution Reaction (HER) is the main reason for the higher price of pure hydrogen as a fuel. In our present research, we chose the less expensive cesium tungsten bronzes (CTB) doped with various percentages of vanadium (5 mol% - 20 mol%) to study their HER performance. The materials were prepared hydrothermally at 180 °C at different reaction times. XRD revealed that, upon increasing the vanadium amount, the hexagonal phase of the CTB is transformed to the cubic phase at a higher reaction time. However, the hexagonal phase was retained after vanadium introduction with a lower reaction time. FT-IR, Raman, EDX, SIMS, XPS, and XRF spectroscopy confirmed the incorporation of vanadium into the bronze system. Vanadium-doped samples showed enhanced HER activity compared to the pure CTB. The 20% vanadium-doped hexagonal bronze showed the best HER performance in 0.5 M H2SO4 among all the vanadium-doped materials, which lowered the HER potential of the pure CTB (-0.665 V vs RHE) to -0.288 V vs RHE at -10 mA cm−2. This increase in activity was correlated with a higher surface area, higher electrochemical surface area, faster reaction kinetics with a lower Tafel slope, and a small charge-transfer resistance of the samples after V5+ incorporation compared to the pure CTB.

Highly efficient photo-degradation for tetracycline elimination in pharmaceutical wastewater by α-Fe2O3/V2O5/BC assisted peroxymonosulfate activation

In this study, a novel α-Fe2O3/V2O5/BC catalyst with highperoxymonosulfate (PMS)activation performance was constructed by co-pyrolysis method and 99.58% of tetracycline is degraded within 120 min. The electrons conversion of Fe-V on biochar surface induces the continuous generation of sulfate radicaland singlet oxygen molecules (1O2).The XPS results show that it is Fe3+and Fe0rather than Fe3+and Fe2+in the iron cycle after the introduction of vanadium, indicating a more efficient electron transfer efficiency between interface. The optical properties characterization and density function theory calculation (DFT) of α-Fe2O3/V2O5/BC reveal that the electrons of the entire α-Fe2O3and the vanadium atoms are redistributed to new molecular orbitals due to strong interfacial chemical bonding, inducing a direct transfer of electrons to generate1O2for tetracycline removal that is the main cause of selective degradation. Besides, the possible degradation mechanism and tetracycline degradation pathways were also proposed. The α-Fe2O3/V2O5/BC maintains a high removal efficiency of tetracycline only decrease by 7.09% after six cycles. This study provides a better strategy and recyclable purification material for the efficient treatment of antibiotic pharmaceutical wastewater.

Modulating MoS2 nanostructure by vanadium incorporation for high-efficiency hydrogen evolution reaction

In this work, we reported a facile approach to fabricate molybdenum sulfide (MoS2) electrocatalyst with the introduction of vanadium(V) for improved catalytic performance. The morphology of prepared samples can be characterizated by SEM observation. The XRD and XPS spectra further reveal that the proper amount of vanadium introduction can effectively prompt the increase of crystallinity and formation of edge-terminated structure in MoS2 nanostructure. The experimental results display that the morphology of MoS2 can be modulated by various amounts of V incorporation. The conductivity of prepared samples is increased by incorporating a certain amount of graphene. MoS2 nanostructure with 20% V incorporation shows excellent catalytic performance, and the corresponding mechanism is also discussed. The electrochemical performance of 20%V-MoS2 can be further improved by the introduction of appropriate graphene. Compared with pure MoS2 samples, 20%V-MoS2/Graphene7.5 shows a small resistance and excellent cycling stability in the acidic electrolyte, as well as the overpotential at 10 mA decreases from 213 mV to 168 mV.

Vanadium doped Ni/Al2O3: Efficient and coke resistant catalysts for methane dry reforming

The effects of vanadium promotion on γ-alumina supported nickel catalysts were investigated for Methane Dry reforming (MDR). Three samples were compared: bare Ni/Al2O3 as reference, Ni-V/Al2O3, and Ni-V-Ca/Al2O3 to evaluate whether the introduction of these additional doping agents can further improve the activity and the stability of the catalyst. The catalysts were synthetized via incipient wetness impregnation and tested in MDR at 650 °C, first with a reagents ratio CH4:CO2:He= 1:1:18 and then CH4:CO2:He= 1:1:8. Fresh and spent catalysts were studied by different techniques, such as N2 physisorption, TPR, XRD, DRUV–VIS, SEM-EDX, O2 chemisorption and TPO. In diluted gases conditions, the introduction of vanadium is crucial to hinder catalyst deactivation by coke deposition. In particular, the formation of nanotubes was reduced, with an increase in hydrogen yield. When coupled with calcium, selectivity toward hydrogen/syngas production was improved. Under concentrated gases was highlighted how vanadium is fundamental for a higher activity, with an increase of 30% and 15% in CH4 and CO2 conversions, if compared with the non-doped catalyst.

Revealing the significance of the influence of vanadium on the mechanical properties of cast iron for castings for machine-building purpose

The object of study in this work is cast iron with lamellar graphite, modified with two types of modifiers – FeSi75 and FeSi40V7. In this work, the influence of vanadium on the mechanical properties of cast iron used for castings for engineering purposes was determined. The existing problem lies in the fact that ignorance of the influence of the alloying element on the mechanical properties of the alloy does not allow determining its consumption rates during the melting process. This can lead to unnecessary costs for materials for melting and casting, and not be justified in terms of the expected improvement in properties. To determine the effect of vanadium on properties, three indicators of the quality of cast iron are considered: tensile strength, stiffness, and a generalized quality index for mechanical properties. A decision is proposed on the procedure for checking the significance of the influence of vanadium within the considered range of variation V=0.04–0.078 % on these indicators. It has been established that the introduction of vanadium into cast iron as part of the FeSi40V7 modifier leads to a decrease in the tensile strength by 4 %, but to an increase in rigidity by 2 %. A significant influence of vanadium with a probability of 95 % was also established with respect to the generalized quality indicator for mechanical properties – the introduction of vanadium contributes to a drop in this indicator by about 5 %. As a result, it was concluded that the use of vanadium in the composition of FeSi40V7 within the final content in cast iron at the level of 0.04–0.078 % can be expedient only if it is necessary to increase the hardness of cast iron due to the promotion of carbide formation during alloy crystallization. The presented study will be useful for machine-building enterprises that have foundries in their structure, where cast iron is smelted for the manufacture of castings.

Vanadium‐modified hard carbon spheres with sufficient pseudographitic domains as high‐performance anode for sodium‐ion batteries

AbstractHard carbons are promising anode materials for sodium‐ion batteries. To meet practical requirements, searching for durable and conductive carbon with a stable interface is of great importance. Here, we prepare a series of vanadium‐modified hard carbon submicrospheres by using hydrothermal carbonization followed by high‐temperature pyrolysis. Significantly, the introduction of vanadium can facilitate the nucleation and uniform growth of carbon spheres and generate abundant V–O–C interface bonds, thus optimizing the reaction kinetic. Meanwhile, the optimized hard carbon spheres modified by vanadium carbide, with sufficient pseudographitic domains, provide more active sites for Na ion migration and storage. As a result, the HC/VC‐1300 electrode exhibits excellent Na storage performance, including a high capacity of 420 mAh g−1 at 50 mA g−1 and good rate capability at 1 A g−1. This study proposes a new strategy for the synthesis of hard carbon spheres with high tap density and emphasizes the key role of pseudographitic structure for Na storage and interface stabilization.

Regulating the electronic structure of Ni3S2 nanorods by heteroatom vanadium doping for high electrocatalytic performance

The exploration of high-performance, inexpensive noble-metal-free electrocatalysts for the oxygen evolution reaction (OER) may be critical for sustainable mass production of renewable energy. In this study, vanadium-doped Ni3S2 nanorod arrays grown on three-dimensional nickel foam (V-Ni3S2/NF) were designed and synthesized by a facile hydrothermal route. Electrochemical measurements showed that the sample with an appropriate amount of V doping (S: V mass ratio of 25:3) exhibited superior OER performance, with an overpotential of 189 mV at a current density of 100 mA cm−2 and a low Tafel slope of 148.87 mV dec−1. The improved catalytic performance can be attributed to the optimization of the electronic structure resulting from enhanced electron transfer due to doping with impurity atoms. Detailed characterization showed that homogeneous V doping changed the morphology of Ni3S2 from nanosheets to nanorods; it also introduced additional catalytic active sites and significantly improved the electrocatalytic activity for the OER. In addition, V-Ni3S2/NF exhibited excellent electrocatalytic stability compared to noble-metal (IrO2) electrocatalysts. The introduction of vanadium suggests a new approach to the design of high-performance OER catalysts in alkaline medium.

Two Polyoxometalate-Based Hybrid Compounds Modified by Iron Schiff Base Complexes: Syntheses, Crystal structures, Cyclic Voltametric Studies and Nonlinear Optical Properties.

Two new polyoxometalate (POM)-based hybrid compounds modified by a Schiff base, [Fe(DAPSC)(H2 O)2 ]2 [HPMo2 V Mo10 VI O40 ] ⋅ 5H2 O (1) and [Fe(DAPSC)(H2 O)]2 [HPV3 IV Mo4 V Mo7 VI O42 ] ⋅ 6H2 O (2), (DAPSC=2,6-diacetylpyridine bis-(semicarbazone)), have been successfully constructed from typical Keggin POMs, iron ions, and DAPSC ligands under hydrothermal condition. Structural analysis demonstrates that the Fe-Schiff base ligand units are free from polyacid anions in compound 1. While in compound 2, the Fe-Schiff base ligand units are bridged with polyacid anions via Fe-O bonds to emerge a stable double-supported skeleton. Noticeably, owing to the introduction of vanadium in H5 PMo10 V2 O40 ⋅ 32.5H2 O, a divanadium-capped configuration is shaped in compound 2. Besides, the third-order nonlinear optical (NLO) properties of two compounds were explored. It should be noted that both compounds 1 and 2 have two-photon absorption properties, which indicates that the two compounds are potential nonlinear optical materials.

Efficient oxidative degradation of fluconazole by a heterogeneous Fenton process with Cu-V bimetallic catalysts

In this study, a novel Cu-V bimetallic catalyst (CuVOx) with abundant surface defects was successfully synthesized by hydrothermal method. Degradation experiment of emerging pollutant fluconazole confirmed that CuVOx exhibited higher catalytic activity, wider pH applicability and more satisfactory reusability than monometallic copper compounds. Electron paramagnetic resonance and radical quenching tests indicated that surface hydroxyl groups play a crucial role in the degradation of contaminants. By the introduction of vanadium into copper-based materials, several surface properties that are closely related to the reactivity of the copper catalysts such as adsorption capacity, surface defects, and active sites concentration were improved. It was also found that the electron-rich center around Cu/V active sites and surface oxygen vacancies are responsible for the rapid dissociation of H2O2 and the efficient catalytic oxidation of fluconazole in CuVOx Fenton system. We also applied CuVOx Fenton to the degradation of various refractory organic pollutants, further confirming its excellent removal and detoxification efficiency for organic pollutants in the aquatic environment.

THE INFLUENCE OF VANADIUM AND CHROMIUM CITRATES ON THE ANTIOXIDANT SYSTEM IN THE BLOOD OF RATS WITH EXPERIMENTAL DIABETES

Introduction. Today, diabetes mellitus is one of the most common metabolic diseases. Therefore, there is a growing interest in finding new pharmacological agents for prevention and treatment of diabetes. Aim. To determine the influence of vanadium and chromium citrates on the state of the antioxidant system in the rats’ blood with experimentally induced diabetes. Method s . We determined the content of peroxide oxidation products of lipids in the blood — lipid hydroperoxides and thiobarbituric acid reactive substances; activity of enzymes of antioxidant protection — catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase and the content of reduced glutathione. Results. Hyperglycemia is observed in the blood of the rats with alloxan diabetes and lipid peroxide oxidation — lipid hydroperoxides and thiobarbituric acid reactive substances increased. In addition, for experimental diabetes in the blood of animals, the activity of catalase, superoxide dismutase, glutathione reductase and the content of reduced glutathione decreased, but the content of glutathione peroxidas increased. The content of products of lipid peroxidation and the activity of antioxidant enzymes became normal after the introduction of vanadium and chromium citrates into the diet of the animals with diabetes mellitus. Conclusion. Introduction of citrates of vanadium and chromium into the diet of animals with alloxan-induced diabetes causes the normalization of the state of the antioxidant system in the blood. Obtained results can form the basis for the development of methods and tools for preventing diabetes mellitus.

Electrochemical properties of LiNi0.6Co0.12Mn0.2V0.08O2 as the tetrad cathode material of lithium-ion battery under high cut-off voltages

In the study, a new kind of tetrad cathode lithium-ion battery material (LiNi0.6Co0.2-xMn0.2VxO2 (x = 0, 0.06, 0.08, 0.10)) was synthesized and then characterized by XRD, XPS, SEM, EDS, electrochemical measurements, CV, and EIS. The homogenous distribution of vanadium element on the materials was verified and the layer crystal structure was not changed when x = 0.08. XPS results indicated that suitable vanadium substitution reduced cation mixing on the surface due to the lower content of Ni2+. Electrochemical measurements confirmed that LiNi0.6Co0.12Mn0.2V0.08O2 had the highest initial coulombic efficiency (80 % at 0.05 C), rate capacity (129.4 mAh/g at 5 C), and cycling performance (92.6% at 1 C) at the cutoff voltage of 4.6 V, which were much better than those of LiNi0.6Co0.2Mn0.2O2. LiNi0.6Co0.12Mn0.2V0.08O2 showed good dynamic properties in CV and EIS tests. The results of XRD and SEM for cycled electrodes showed that the introduction of vanadium could significantly relieve structural damages of LiNi0.6Co0.2Mn0.2O2 during charge/discharge processes. This study indicated that controlled vanadium introduction could effectively improve the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 for developing the high-voltage cathodes for high-energy lithium-ion batteries.

Role of Vanadium in Aluminum Electrolyzer Melts

The article provides results of testing excess introduction of vanadium into a molten aluminum cell through baked anodes. This stage of special technology is preliminary and required before the boriding heavy metal impurities in molten aluminum. The requirement of a preliminary stage is dictated by the presence of an insulating aluminum carbide layer on the surface of the carbon hearth that reduces the efficiency of aluminum boriding technology. The specific properties of vanadium and its compounds make it possible to organize chemical cleaning of the cathode from an Al4C3 layer, replacing it with a VC substrate. It is shown that with constant introduction of vanadium into melt dynamic equilibrium is established between vanadium and its compounds entering the cell and removed from it. Stabilization of a VC-coating requires organization of boriding technology for molten electrolyte and aluminum, creating a viscous low-mobility layer of a metal-boride Me–B suspension wetted with aluminum on the hearth.

Synthesis and characterization of TiO2-V2O5-MCM-41 for catalyzing transesterification of dimethyl carbonate with phenol

A series of TiO2-V2O5-MCM-41 molecular sieve catalysts were prepared by the impregnation method. The prepared catalysts were characterized by different techniques including X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and N2 adsorption–desorption. These catalysts were applied in the catalytic synthesis of diphenyl carbonate (DPC) by the transesterification of dimethyl carbonate (DMC) with phenol. The synthesis results indicated that the catalysts possessed the high specific surface area and large pore volume and included titanium with four ligands. Due to the vanadium introduction into Ti-MCM-41, the catalytic activity was promoted, by-products were reduced, and the catalytic activity and stability of the catalyst were significantly improved. With 10%V-20%Ti-MCM-41 catalyst, the optimal synthesis results including the conversion rate of DMC of 33.88%, the selectivity of DPC of 35.84%, and the yield of DPC of 12.14% were obtained.

Enhancing CO2 electrolysis performance with vanadium-doped perovskite cathode in solid oxide electrolysis cell

CO2 electrolysis using solid oxide electrolysis cells (SOECs) is a promising technology for sustainable conversion of CO2 to chemicals and the intermittent renewable electricity storage. However, the lack of highly active and stable cathode inhibits the development of CO2 electrolysis in SOECs for practical applications. Herein, La0.5Sr0.5Fe1-xVxO3-δ/Ce0.8Gd0.2O2-δ (LSFVx/GDC, x = 0, 0.05, 0.10, 0.15) composite with high catalytic activity and operating stability is exploited as cathode material of SOEC for CO2 electrolysis. The introduction of vanadium promotes the formation of oxygen deficiencies in LSFVx/GDC, and alters the electronic structure of Fe, thus greatly enhances the adsorption and dissociation of CO2. Compared with the LSF/GDC cathode, the LSFV0.05/GDC cathode achieves ca. 51.2% increase in current density at 1.6 V and 800 °C.

Effect of Vanadium Introduction on the Activity of NiMo/Al2O3 Catalysts in the Hydrotreating of Diesel Fractions

The influence of the introduction of V2O5 into NiMo/Al2O3 catalysts on their activity in hydrodesulfurization (HDS) and hydrogenation reactions of the components of petroleum fractions has been studied. The activity of the synthesized catalysts has been determined in the straight-run diesel and light coker gas oil hydrotreating processes in a flow-through unit under hydrogen pressure. The most active catalyst for HDS and hydrogenation of polycyclic aromatic hydrocarbons has been synthesized using VMo12 heteropoly compounds: the activity increases by 6–10 and 11–13 wt % in HDS and PAH hydrogenation, respectively, at different temperatures. It has been shown that the activity of the regenerated catalyst further impregnated with the vanadium compound in HDS and PAH hydrogenation increases by 2–5 rel. %, as compared to the regenerated catalyst.

Quality of Metal Deposited Flux Cored Wire With the System Fe-C-Si-Mn-Cr-Mo-Ni-V-Co

Studied the effect of the introduction of vanadium and cobalt into the charge powder fused wire system Fe-C-Si-Mn-Cr-Ni-Mo-V, used in cladding assemblies and equipment parts and mechanisms operating under abrasive and abrasive shock loads. the cored wires samples were manufactured in the laboratory conditions and using appropriate powder materials and as a carbonfluoride contained material were used the dust from gas purification of aluminum production, with the following components composition, %: Al2O3 = 21-46.23; F = 18-27; Na2O = 8-15; K2O = 0.4-6; CaO = 0.7-2.3; Si2O = 0.5-2.48; Fe2O3 = 2.1-3.27; C = 12.5-30.2; MnO = 0.07-0.9; MgO = 0.06-0.9; S = 0.09-0.19; P = 0.1-0.18. Surfacing was produced on the St3 metal plates in 6 layers under the AN-26C flux by welding truck ASAW-1250. Cutting and preparation of samples for research had been implemented. The chemical composition and the hydrogen content of the weld metal were determined by modern methods. The hardness and abrasion rate of weld metal had been measured. Conducted metallographic studies of weld metal: estimated microstructure, grain size, contamination of oxide non-metallic inclusions.Metallographic studies showed that the microstructure of the surfaced layer by cored wire system Fe-C-Si-Mn-Cr-Mo-Ni-V-Co is uniform, thin dendrite branches are observed. The microstructure consists of martensite, which is formed inside the borders of the former austenite grain retained austenite present in small amounts in the form of separate islands, and thin layers of δ-ferrite, which is located on the borders of the former austenite grains.Carried out an assessment the effect of the chemical composition of the deposited metal on the hardness and wear and hydrogen content. In consequence of multivariate correlation analysis, it was determined dependence to the hardness of the deposited layer and the wear resistance of the mass fraction of the elements included in the flux-cored wires of the system Fe-C-Si-Mn-Cr-Mo-Ni-V-Co. The calculated value of the average approximation error suggests that the dependence is adequate and can be used to determine the resulting indicators. These dependencies can be used to predict the hardness of the deposited layer and its wear resistance while changing the chemical composition of the weld metal.

Study of the properties of flux cored wire of Fe-C-Si-Mn-Cr-Mo-Ni-V-Co system for the strengthening of nodes and parts of equipment used in the mineral mining

The effect of the introduction of vanadium and cobalt into the charge of the powder surfacing wire of Fe-C-Si-Mn-Cr-Mo-Ni system is studied. In the laboratory conditions, the samples of flux cored wires were produced. The surfacing made by the prepared wire was produced under the flux AN-26C, on the plates of steel St3 in 6 layers with the help of ASAW-1250 welding tractor. Reduction of carbon content in the deposited layer to 0.19-0.2% with simultaneous change in the content of chromium, nickel, molybdenum and other elements present in it contributes to the enlargement of the martensite needles and the increase in the size of the former austenite grain. The obtained dependences of hardness of the deposited layer and its wear resistance on the mass fraction of elements, included in the composition of powder wires of the proposed system, can be used to predict the hardness of the welded layer and its wear resistance under different operating conditions for mining equipment and coal mining equipment.