Vanadium Molybdenum Research Articles

Catalytic activity of MoO3:V2O5 mixed oxides towards oxidation reactions: the nature of catalytic centers

Singlet oxygen emission and peroxide generation at the surface of molybdenum–vanadium oxides evidenced that the catalytic activity of a MoO3:V2O5 mixed oxide at 70–175 °C was governed by the formation of peroxo groups in the interaction of molecular oxygen with adjacent Viv surface centers; the thermolysis of these groups yielded singlet oxygen capable of oxidizing selectively alcohols to aldehydes.

Vanadium Molybdenum Disulfide Nanosheets Anchoring on Carbon Cloth as High-Energy Density Cathode for Magnesium-Lithium Hybrid Batteries.

Magnesium-lithium-ion hybrid batteries (MLIBs) have gained significant attention since the combination of a dendrite-free and low-cost magnesium anode with lithium-ion storage cathodes. However, the lack of high-performance cathodes has severely hindered their development, limited by the lower operating voltages of electrolytes. Herein, vanadium molybdenum disulfide nanosheets anchoring on flexible carbon cloth (VMS@CC) are constructed as high-performance cathodes for MLIBs, which inherit the electrochemical properties of high-voltage VS2 and high-capacity MoS2, simultaneously. By adjusting the V and Mo atomic ratio, the VMS@CC cathode for MLIBs delivers a record maximum energy density of 275.5 Wh kg-1 with a high working voltage of 1.07 V at 50 mA g-1. Meanwhile, under the synergistic effects of the conductive carbon cloth matrix, abundant hetero-interfaces and defects, as well as expanded interlayer spacing, the VMS@CC cathode displays superior rate capability and long-term cycling stability. Ex situ analyses demonstrate the VMS nanosheets cathode exhibits a Li+/Mg2+ co-insertion/extraction mechanism in MLIBs, following the in situ insertion of organic species in the hybrid electrolyte during the aging process. The fabricated flexible cathode herein provides a new insight into the construction of high-energy density cathodes for MLIBs.

Molybdenum–Vanadium Oxide Clusters: Syntheses, Structures and Antibacterial Properties

The design and synthesis of polyoxometalates (POMs), a type of inorganic compounds, are of great interest due to their interesting structural properties as well as their extensive theoretical and practical applications in catalysis, electrical conductivity, magnetism, optics and medicine. Therefore, in this study two molybdovanadates [Cu(phen)2]3[Mo6V2O26]·4H2O and [Cu(bpy)2]3[Mo6V2O26]·4H2O have been prepared by the reaction of the [Mo6V2O26]6- anion with Cu(CH3COO)2 and 1,10-phenanthroline/2,2'-bipyridine in aqueous medium; characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance (1H NMR), Inductively coupled plasma mass spectrometry (ICP-MS), Thermogravimetric Analysis (TGA) and elemental analysis. The compounds show antibacterial activity against Escherichia coli (E. Coli) and Staphylococcus aureus (S. Aureus).

Cryogenic Treatment of Chromium–Molybdenum–Vanadium Steels: Unveiling Microstructural Features and Improved Mechanical Properties

Cryogenic Treatment of Chromium–Molybdenum–Vanadium Steels: Unveiling Microstructural Features and Improved Mechanical Properties

Pillared Vanadium Molybdenum Disulfide Nanosheets: Toward High-Performance Cathodes for Magnesium-Ion Batteries.

If magnesium-ion batteries (MIBs) are to be seriously considered for next-generation energy storage, then a number of major obstacles need to be overcome. The lack of reversible cathode materials with sufficient capacity and cycle life is one of these challenges. Here, we report a new MIB cathode constructed of vertically stacked vanadium molybdenum sulfide (VMS) nanosheets toward addressing this challenge. The integration of vanadium within molybdenum sulfide nanostructures acts so as to improve the total conductivity, enhancing charge transfer, and to produce abundant lattice defects, improving both the accommodation and transport of Mg2+. Additionally, electrolyte additive-induced interlayer expansion provides a means to admit Mg2+ cations into the electrode structure and thus enhance their diffusion. The VMS nanosheets are capable of exhibiting capacities of 211.3 and 128.2 mA h g-1 at current densities of 100 and 1000 mA g-1, respectively. The VMS nanosheets also demonstrate long-term cycling stability, retaining 82.7% of the maximum capacity after 500 cycles at a current density of 1000 mA h g-1. These results suggest that VMS nanosheets could be promising candidates for high-performance cathodes in MIBs.

Electrocatalysts for Zinc-Air Batteries Featuring Single Molybdenum Atoms in a Nitrogen-Doped Carbon Framework.

Bifunctional catalysts can facilitate two different electrochemical reactions with conflicting characteristics. Here, a highly reversible bifunctional electrocatalyst for rechargeable zinc-air batteries (ZABs) is reported featuring a "core-shell structure" in which N-doped graphene sheets wrap around vanadium molybdenum oxynitride nanoparticles. Single Mo atoms are released from the particle core during synthesis and anchored to electronegative N-dopant species in the graphitic shell. The resultant Mo single-atom catalysts excel as active oxygen evolution reaction (OER) sites in pyrrolic-N and as active oxygen reduction reaction (ORR) sites in pyridinic-N environments. ZABs with such bifunctional and multicomponent single-atom catalysts deliver high power density (≈376.4mWcm-2 ) and long cycle life of over 630h, outperforming noble-metal-based benchmarks. Flexible ZABs that can tolerate a wide range of temperatures (-20 to 80°C) under severe mechanical deformation are also demonstrated.

Identification of Substitutional Solid Solutions Derived from Molybdenum–Vanadium Oxides Using Infrared Spectroscopy

Identification of Substitutional Solid Solutions Derived from Molybdenum–Vanadium Oxides Using Infrared Spectroscopy

Synergetic effect of ternary MnVMo-oxide electrode by hydrothermal method for high-performance asymmetric supercapacitor

The binder-free deposition facilitates fast electron transfer and smoothens the diffusion path of electrolyte ions into the matrix of electrode material. Herein, the ternary metal oxides, such as manganese vanadium molybdenum oxide (MnVMo-oxide) is directly deposited on nickel foam by a single-step hydrothermal method. X-ray diffraction study confirms formation of MnVMo-oxide phase. The X-ray photoelectron spectroscopy confirms the Mn, V, and Mo are in the +2 (and +3), +5, and +6 oxidation states. Deposition time variation results, change in nanostructures from nanoparticle-assembled sheets to rectangular nanosheets, also the size of micro rods. The porous microrods formed with uneven quasi-rectangular shaped nanosheets of MnVMo-oxide exhibit high areal capacitance of 814.5 mFcm−2 (as compared to other electrodes) measured in 1 M KOH electrolyte at 3 mAcm−2 current density. The enhanced capacitance of the MnVMo-8 electrode is due to the dominance of the diffusion process over the capacitive-controlled contribution and high diffusion coefficient. The fabricated asymmetric supercapacitor device MnVMo-oxide//activated carbon shows good areal capacitance of 40 mFcm−2 with 0.025 mWhcm−2 energy at 1.5 mWcm−2 power density measured at 2 mAcm−2 current density, and cyclic stability of about 71.45 % (Coulombic efficiency of 98 %) quantified up to ∼9000 consecutive cycles.

Molybdenum Vanadium Oxides as Intercalation Hosts for Chloroaluminate Anions

Driven by the cost and scarcity of Lithium resources, it is imperative to explore alternative battery chemistries such as those based on Aluminum (Al). One of the key challenges associated with the development of Al-ion batteries is the limited choice of cathode materials. In this work, we explore an open-tunnel framework-based oxide (Mo3VOx) as a cathode in an Al-ion battery. The orthorhombic phase of molybdenum vanadium oxide (o-MVO) has been tested previously in Al-ion batteries but has shown poor coulombic efficiency and rapid capacity fade. Our results for o-MVO are consistent with the literature. However, when we explored the trigonal polymorph of MVO (t-MVO), we observe stable cycling performance with much improved coulombic efficiency. At a charge–discharge rate of ~0.4C, a specific capacity of ~190 mAh g−1 was obtained, and at a higher rate of 1C, a specific capacity of ~116 mAh g−1 was achieved. We show that differences in synthesis conditions of t-MVO and o-MVO result in significantly higher residual moisture in o-MVO, which can explain its poor reversibility and coulombic efficiency due to undesirable water interactions with the ionic liquid electrolyte. We also highlight the working mechanism of MVO || AlCl3–[BMIm]Cl || Al to be different than reported previously.

Phase Transfer Catalytic Oxidation of Cyclopentene to Glutaraldehyde by Vanadium Molybdenum Heteropolyacid Salts

Phase Transfer Catalytic Oxidation of Cyclopentene to Glutaraldehyde by Vanadium Molybdenum Heteropolyacid Salts

10-Molybdo-2-vanadophosphoric acid derived (V) MoS2 microflowers @ V2CTx MXene designed 3D@2D nanoarchitecture for high-performance aqueous supercapacitors

Polyoxometalates (POMs) are emerging redox active materials having great potential for energy storage. Normally, POMs are directly anchored to substrates, however we looked into a novel feature of POM chemistry by employing them as precursor for metal sulphide 3D microflower arrangements without the use of a template. High surface area, outstanding electrical conductivity, and exceptional structural stability are all characteristics of 2D materials like MXenes; nevertheless, their direct use is constrained by poor specific capacitance as a result of layer restacking. Transition Metal sulphides (TMDs), on the other hand, have a high surface area but a poor conductivity. Layer restacking will be prevented by an MXene-TMDs nanocomposite, which will also increase TMDs' conductivity. Here, we report MXene-TMDs nanocomposite (MV) with MXene intercalated vanadium molybdenum sulphide (VMD) microflowers using 10-molybdo-2-vanadophosphoric acid. Due to faster ionic diffusion, higher electrochemically active surface area, and more active sites, MV exhibits good electrochemical performance. Additionally, the MV||MV cell offers outstanding cycling stability (96 % capacitance retention after 8000 cycles @ 2 A g−1) and performs well up to 0.9 V, delivering a maximum energy density of 28.96 Wh kg−1 @ 232.35 W kg−1. This research investigates how POMs affect the atomic ratio and morphology of final product.

Synthesis and characterization of (Mo0.52V0.38W0.1)2O5 used as a catalyst in the oxidative dehydrogenation of ethane

This work presents a study of mixed molybdenum vanadium and tungsten oxides applied to oxidative dehydrogenation of ethane (ODE). Different oxides were prepared by a microwave-assisted hydrothermal method using oxalic acid as a reducing agent to obtain a crystalline phase of composition (Mo0.52V0.38W0.1)2O5. The materials were studied by XRF, BET, X-ray powder diffraction (XRD), transmission electron microscopy, IR, UV–Vis, TPR-H2 and XPS spectroscopy. The structure with space group C2/m is closely related to that of R–Nb2O5 with cell parameters a ​= ​1215.1 p.m., b ​= ​374.2 p.m., c ​= ​402.0 p.m., and β ​= ​90.70°. This phase is stable under reaction and active and selective to ethylene in the ODE reaction. Comparison with the literature indicates that R–Nb2O5-type matrices constitute an alternative to Mo5O14-type oxides to control the selectivity of active species in ODE.

Steady State Performance Evaluation of Noble-Metal Free Bifunctional Electrode for Overall Water Splitting

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency. This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst that is cost effective and can show a comparable HER (Hydrogen Evolution Reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen Evolution Reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance. In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering. This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear Sweep Voltammetry)/CV (Cyclic Voltammetry). This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.

Engineering Transition Metals As Noble-Metal Free Bifunctional Electrode for Overall Water Splitting

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency.[1] This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst which can show a comparable HER (Hydrogen evolution reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen evolution reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance.[2] In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering.[3] This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear sweep voltammetry)/CV (Cyclic Voltammetry).[4] This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.[1] J. Zhang et al., “Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics,” Nat. Commun., vol. 8, no. May, pp. 1–8, 2017, doi: 10.1038/ncomms15437.[2] L. A. Santillán-Vallejo et al., “Supported (NiMo,CoMo)-carbide, -nitride phases: Effect of atomic ratios and phosphorus concentration on the HDS of thiophene and dibenzothiophene,” Catal. Today, vol. 109, no. 1–4, pp. 33–41, 2005, doi: 10.1016/j.cattod.2005.08.022.[3] B. Wei et al., “Bimetallic vanadium-molybdenum nitrides using magnetron co-sputtering as alkaline hydrogen evolution catalyst,” Electrochemistry Communications, vol. 93. pp. 166–170, 2018, doi: 10.1016/j.elecom.2018.07.012.[4] S. Anantharaj and S. Kundu, “Do the Evaluation Parameters Reflect Intrinsic Activity of Electrocatalysts in Electrochemical Water Splitting?,” ACS Energy Lett., vol. 4, no. 6, pp. 1260–1264, 2019, doi: 10.1021/acsenergylett.9b00686. Figure 1

Reversible and rapid calcium intercalation into molybdenum vanadium oxides

Looming concerns regarding scarcity, high prices, and safety threaten the long-term use of lithium in energy storage devices. Calcium has been explored in batteries because of its abundance and low cost, but the larger size and higher charge density of calcium ions relative to lithium impairs diffusion kinetics and cyclic stability. In this work, an aqueous calcium-ion battery is demonstrated using orthorhombic, trigonal, and tetragonal polymorphs of molybdenum vanadium oxide (MoVO) as a host for calcium ions. Orthorhombic and trigonal MoVOs outperform the tetragonal structure because large hexagonal and heptagonal tunnels are ubiquitous in such crystals, providing facile pathways for calcium-ion diffusion. For trigonal MoVO, a specific capacity of ∼203 mAh g-1 was obtained at 0.2C and at a 100 times faster rate of 20C, an ∼60 mAh g-1 capacity was achieved. The open-tunnel trigonal and orthorhombic polymorphs also promoted cyclic stability and reversibility. A review of the literature indicates that MoVO provides one of the best performances reported to date for the storage of calcium ions.

Енергозберігаюча термічна обробка легованих сталей зі змішаною структурою

The purpose of the work was to research ways to reduce the duration of the intermediate heat treatment mode of alloy steels while ensuring the required level of properties and reducing energy costs. For further mechanical processing of alloy rolled metal, it is necessary to obtain the original rolled product with a structure that has high plasticity and low hardness. In order to achieve the required mechanical properties, a special softening heat treatment is carried out - annealing at subcritical temperatures (A1 - 25...40 °С) with a long exposure. Thanks to annealing, structural transformations take place and the resulting structure has a granular morphology. Research has established that in steels with a mixed structure during annealing, structural transformations begin with thermodynamically less stable structures. For medium-carbon steels alloyed with such elements as chromium, molybdenum, vanadium, increasing the cooling rate after hot rolling by ~1.5 times makes it possible to obtain a structure that is more susceptible to annealing. Thus, for chrome-molybdenum steel, the structure consists of at least 80% bainite, ~15% ferrite and 5% pearlite. For chromium molybdenum vanadium steel, the basis of the structure is bainite (~90%), martensite (~5%) and ferrite (up to 5%). In the resulting structures, upon subsequent annealing, structural transformations occur at reduced temperatures and require a shorter exposure time. The values of hardness and strength of the studied steels processed under the reduced regime decrease by 15-30%, and the plasticity indicators increase by ~50%. Obtaining such a structure after rolling makes it possible to speed up the intermediate thermal softening treatment, thereby reducing energy costs, and ensuring high plasticity of steel before mechanical processing (stamping, forging, etc.)

The Positive Role of Nanometric Molybdenum-Vanadium Carbides in Mitigating Hydrogen Embrittlement in Structural Steels.

The influence of hydrogen on the fracture toughness and fatigue crack propagation rate of two structural steel grades, with and without vanadium, was evaluated by means of tests performed on thermally precharged samples in a hydrogen reactor at 195 bar and 450 °C for 21 h. The degradation of the mechanical properties was directly correlated with the interaction between hydrogen atoms and the steel microstructure. A LECO DH603 hydrogen analyzer was used to study the activation energies of the different microstructural trapping sites, and also to study the hydrogen eggresion kinetics at room temperature. The electrochemical hydrogen permeation technique was employed to estimate the apparent hydrogen diffusion coefficient. Under the mentioned hydrogen precharging conditions, a very high hydrogen concentration was introduced within the V-added steel (4.3 ppm). The V-added grade had stronger trapping sites and much lower apparent diffusion coefficient. Hydrogen embrittlement susceptibility increased significantly due to the presence of internal hydrogen in the V-free steel in comparison with tests carried out in the uncharged condition. However, the V-added steel grade (+0.31%V) was less sensitive to hydrogen embrittlement. This fact was ascribed to the positive effect of the precipitated nanometric (Mo,V)C to alleviate hydrogen embrittlement. Mixed nanometric (Mo,V)C might be considered to be nondiffusible hydrogen-trapping sites, in view of their strong hydrogen-trapping capability (~35 kJ/mol). Hence, mechanical behavior of the V-added grade in the presence of internal hydrogen was notably improved.

Construction of molybdenum vanadium oxide/nitride hybrid nanoplate arrays for aqueous zinc-ion batteries and reliable insights into the reaction mechanism

Unique CC@a-MVO/MVN HNPAs have been synthesized as an additive- and binder-free cathode for aqueous zinc-ion batteries. Moreover, the reversible formation/decomposition of two different kinds of zinc-containing byproducts is evidently discovered.

Influence of tungsten dopants on structural and electrical properties of sol–gel derived V2O5-MoO3 nanocrystalline films

Tungsten oxide (WO3) doped V2O5·MoO3 thin films deposited on glass substrates using dip coating technique were prepared by a Sol–Gel method. Vanadium pentoxide, Molybdenum oxide and Tungsten oxide powder were used as starting precursors. The influence of different doping percentages of (W) has been investigated in X-ray diffraction, High-resolution transmission electron microscopy and electrical measurement. The structure of the obtained nanocrystals were identify by using X-ray diffraction and transmission electron micrograph. The obtained nanorods have lengths up to 220 nm and width of 15–45 nm. The electrical conductivity applied on the sample under investigation. By increasing tungsten (W) concentration the electrical conductivity was found to be increased and the activation energy decreased. Non-adiabatic SPH was found by analysis the electrical conduction.

First-principles study on XV2S4 (X = Ni, Cr, and Mo) counter electrode for dye-sensitized solar cells

Structural, electronic, and optical properties of ternary vanadium sulfides, XV2S4 (X = Ni, Cr, and Mo), are investigated using first-principles calculations based on density functional theory (DFT) method. The structural parameters, band structures, density of states (DOS), absorption coefficient, and conductivity are reported to discuss the properties of XV2S4 (X = Ni, Cr, and Mo) as potential Pt-free counter electrode for dye-sensitized solar cell (DSSC). Generally, nickel vanadium sulfide (NiV2S4) is predicted to be a good candidate as a counter electrode compares with chromium vanadium sulfide (CrV2S4) and molybdenum vanadium sulfide (MoV2S4) due to its ability to provide high electron density around Fermi level and high conductivity.