Vanadium Molybdenum Oxide 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.

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).

Contribution of Ca and V to enhancing coking-resistance and stability of MoV/CaO-intercalated montmorillonite catalyst in deoxydehydration of glycerol

Glycerol can be converted to allyl alcohol via deoxydehydration using molybdenum-vanadium, rhenium and iron based catalysts. However, the dehydration causes severe coking at strong acid sites on the surface of catalyst. Molybdenum-vanadium oxide supported on calcium oxide-intercalated montmorillonite (MoV-CaMMT) was prepared by oxalate anion intercalation followed by impregnation. MoV-CaMMT displayed the best catalytic performance of 86.5% glycerol conversion and good stability in 5 h. Correlating the results of XRD, XPS and TG analysis, it can be demonstrated that the addition of CaO in the catalyst preparation is conducive to the crystallization and dispersion of vanadium oxides, and reduces the acid strength, while the presence of a few vanadium dioxide and the stable conversion of V4+ and V5+ are the reasons for enhancing coking-resistance of MoV-CaMMT. Additionally, NH3-TPD analysis proved the coexistence of weak and strong acid sites in MoVOx, which are conducive to the formation of acetol.

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.

DEPENDENCE OF ACTIVITY OF BINARY Mo-V-O CATALYSTS IN THE REACTION OF DEHYDROGENATION AND OXIDATION OF ISOPROPYL ALCOHOL ON ACIDIC SURFACE PROPERTIES

The reaction of dehydrogenation and oxidative dehydrogenation of isopropyl alcohol on molybdenum-vanadium oxide catalysts has been studied. It found that the dependences of isopropyl alcohol conversion and propylene yields on the atomic ratio of molybdenum to vanadium in reaction of dehydrogenation of isopropyl alcohol have the form of a curve with two maxima on samples Mo-V=2-8 and Mo-V=6-4. To characterize the acidic properties of the surface of molybdenum-vanadium oxide catalysts, their activity in the reaction of butene-1 isomerization into butenes-2 was also studied. It showed that on molybdenum-vanadium catalysts the dependence of the yield of 2-butenes on the ratio of molybdenum to vanadium also had the form of a curve with two maxima. The activities of molybdenumvanadium oxide catalysts were compared with their acidic properties. It revealed that on binary molybdenum-vanadium oxide catalysts in the reaction of isopropyl alcohol dehydrogenation the increase of surface acidity led to the increase in acetone yield and the decrease in propylene yield. In the reaction of oxidative dehydrogenation of isopropyl alcohol, the increase in surface acidity led to the increase in acetone yield, while propylene yield practically did not change.

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.

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.

Production of the 2,5-Furandicarboxylic Acid Bio-Monomer From 5-Hydroxymethylfurfural Over a Molybdenum-Vanadium Oxide Catalyst.

2, 5-Furandicarboxylic acid (FDCA) is an important bio-monomer that can potentially replace terephthalic acid to synthesize degradable polyesters. Efficient selective oxidation of biomass-based 5-hydroxymethylfurfural (HMF) to FDCA has been a significant but challenging work in the past decades. In this study, a novel molybdenum-vanadium oxide (Mo-V-O) catalyst was prepared by a simple method and showed excellent catalytic activity for converting HMF to FDCA. A high FDCA selectivity of 94.5 and 98.2% conversion of HMF were achieved under the optimal conditions with tert-butyl hydroperoxide as the oxidant. FT-IR, SEM, XRD and TG were applied to investigate the properties of Mo-V-O catalyst. After fitting experimental data with the first-order kinetics equation, the evaluated apparent activation energies of HMF oxidation were obtained. The experimental design and study were carried out by response surface methodology (RSM) to test the effects of reaction conditions on the catalytic process.

Bifunctional Catalyst Derived from Sulfur-Doped VMoOx Nanolayer Shelled Co Nanosheets for Efficient Water Splitting

A novel sulfur-doped vanadium-molybdenum oxide nanolayer shelling over two-dimensional cobalt nanosheets (2D Co@S-VMoOx NSs) was synthesized via a facile approach. The formation of such a unique 2D core@shell structure together with unusual sulfur doping effect increased the electrochemically active surface area and provided excellent electric conductivity, thereby boosting the activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As a result, only low overpotentials of 73 and 274 mV were required to achieve a current response of 10 mA cm-2 toward HER and OER, respectively. Using the 2D Co@S-VMoOx NSs on nickel foam as both cathode and anode electrode, the fabricated electrolyzer showed superior performance with a small cell voltage of 1.55 V at 10 mA cm-2 and excellent stability. These results suggested that the 2D Co@S-VMoOx NSs material might be a potential bifunctional catalyst for green hydrogen production via electrochemical water splitting.

THE ACTIVITY OF MOLYBDENE-VANADIUM OXIDE CATALYSTS IN THE ISOPROPYL ALCOHOL CONVERSION REACTION

The activity of molybdenum-vanadium oxide catalysts in the conversion of isopropyl alcohol has been studied. It was found that acetone and propylene are the main products of the isopropyl alcohol conversion reaction. Studies have shown that the activity of binary molybdenumvanadium oxide catalysts depends both on the reaction conditions and on the atomic ratio of molybdenum to vanadium. It has been shown that molybdenum-vanadium oxide catalysts have a sufficiently high activity in the reaction of propylene and acetone formation and can be used for further modification in order to increase their catalytic activity. Keywords: isopropyl alcohol, acetone, propylene, binary catalysts, molybdenum oxide, vanadium oxide.

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.

Facile Synthesis of Novel V0.13Mo0.87O2.935 Nanowires With High-Rate Supercapacitive Performance.

Binary metal oxides composed of molybdenum–vanadium oxides are promising candidates for supercapacitors. Here, we report the synthesis of one-dimensional V0.13Mo0.87O2.935 nanowires through a facile one-step hydrothermal method. This nanowire presented a high specific capacitance of 394.6 F g−1 (1 mV s−1) as an electrode applied to the supercapacitor. Importantly, this electrode showed a perfect rate capability of 91.5% (2 to 10 A g−1) and a continuous verified outstanding cyclic voltammetry of 97.6% after 10,000 cycles. These superior electrochemical properties make the synthesized V0.13Mo0.87O2.935 nanowires a prospective candidate for high-performance supercapacitors.

Relationship between the catalytic activity and Mo–V surface species in bimetallic catalysts for the oxidative desulfurization of dibenzothiophenic compounds

This work shows the performance of MoOx–VOx based bimetallic catalysts tested on the oxidative desulfurization (ODS) process of refractory dibenzothiophenic compounds using H2O2 as an oxidant. The catalytic activity was related with the oxidation state of molybdenum and vanadium surface species and with the interaction of both metals. The prepared molybdenum–vanadium oxides supported on alumina were subjected to reduction treatments at different temperature to obtain molybdenum and vanadium species with different oxidation state. Catalysts were characterized by their textural properties, scanning electron microscopy–energy dispersive X-ray, X-ray diffraction, temperature programed reduction and X-ray photoelectron spectroscopy. The characterization results showed that metal interactions promote the generation of highly active tetrahedral molybdenum species and isolated vanadium species, which increase the ODS performance of Mo–V based catalysts compared with their respective monometallic catalysts. Also, it was observed that combination of Mo6+, Mo4+ and V4+ superficial species promoted the ODS catalytic activity.

Structural dynamics of molybdenum vanadium oxide (MoVOx)

Molybdenum and vanadium oxides were known to be an effective catalyst for light olefin (propane) activation for conversion to value-added chemicals. However, it is difficult to control the selectivity to desired product whereby subsequent reaction can lead to coking and rapid catalyst deactivation. One of the key ways to improve on the above limitation is to optimise and control the molybdenum phase structure, particularly during catalyst precursor activation stage. This paper demonstrates the combination of optimal in situ activation under different condition and thermal analysis for structural control that can help to guide and gain an insight into the structure–activity relationship of the nanostructured catalyst system. In situ XRD analysis reveals the crystallization of molybdenum vanadium oxide was highly influenced by the activation condition hence exhibiting different structural properties. Activation under Air at 300 °C forms highly crystalline hexagonal phase and transforms to thermodynamically stable orthorhombic (o-MoO3) phase at 450 °C. Activation under inert (helium) reveals the precursor remains amorphous until nanostructuring occurs at 450 °C. The precursor further transforms to the thermodynamically stable crystallized tetragonal phase (Mo5O14) at 500 °C. The obtained structural transition information is important in order to control and identify the catalytic active phase that is suitable for a particular reaction.

High Capacity Rechargeable Magnesium-Ion Batteries Based on a Microporous Molybdenum–Vanadium Oxide Cathode

The three-dimensional microporous framework of the oxide Mo2.5+yVO9+δ (containing Mo5+/6+ and V4+/5+) is defined by three-, six-, and seven-membered ring channels. Due to the oxidation–reduction properties of Mo and V ions and the large open tunnels that can provide a diffusion pathway for small ions, Mo2.5+yVO9+δ has been found to intercalate both Li+ ions, reported previously, and also Mg2+ ions in Mg-ion batteries. Cathodes composed of Mo2.5+yVO9+δ were discharged and charged in Mg-ion cells at current densities ranging from 2 mA/g (C/70) to 10 mA/g (C/12). Mg2+ ions can be inserted into and extracted from MgxMo2.5+yVO9+δ between ∼3.33 and 1.73 V vs Mg/Mg2+ at room temperature, with up to 3.49 Mg2+ ions per formula unit intercalated into the framework, corresponding to a capacity of 397 mAh/g (1st discharge) which is among the highest capacities reported for Mg-based batteries. Powder X-ray diffraction was used to determine the lattice parameters of MgxMo2.5+yVO9+δ (0 < x ≤ 3) compositions prepared by ...

Paramagnetic Centers Created Under Mechanochemical Treatment of Mixed Molybdenum-Vanadium Oxides

Samples of individual and mixed vanadium-molybdenum (V:Mo) oxides xV2O5:(1-x)MoO3, 0 ≤ x ≤ 1, were prepared by the method of mechanochemical activation (MCA). The samples have been characterized by X-ray diffraction (XRD) and X-band electron paramagnetic resonance (EPR) spectroscopy. Prolongation of the treatment duration time in mills led to considerable increase in the V(IV) paramagnetic centers content as well as after additional high temperature annealing at 600 °C. Paramagnetic Mo(V) centers were recorded only in the case of MCA of individual MoO3 oxide. Complexity of the composition of mechanically activated mixed oxides was confirmed with the XRD data. It is shown that in the case of all individual and mixed oxides the content of paramagnetic species increases noticeably with the increase in milling time. The annealing at 600 °C after MCA of mixed oxides forms a new mixed phase of MoV2O8 composition.

Molybdenum–vanadium mixed oxides synthesized by the hydrothermal method

The effect of pressure (5–20 MPa) on the process of hydrothermal synthesis of a molybdenum–vanadium mixed oxide from a molybdenum–vanadium mixed poly(oxyacid) is studied. It is shown that the synthesis product is a solid solution of isomorphically substituted vanadium pentoxide with a pressure-independent composition. With increasing pressure, the degree of crystallinity of the synthesized products increases, concentration of isolated V(IV) ions decreases, habitus of the crystals changes from prismatic to needlelike, and overall dispersity increases. This makes it possible to regard the pressure as a dispersing factor for the synthesis of nanostructured molybdenum–vanadium oxides.

Brannerite-Type Vanadium-Molybdenum Oxide LiVMoO₆ as a Promising Anode Material for Lithium-Ion Batteries with High Capacity and Rate Capability.

Brannerite-type vanadium-molybdenum oxide LiVMoO6 is prepared by a facile liquid-phase method, and its electrochemical properties as anode of lithium-ion batteries are comprehensively studied by means of galvanostatic charge-discharge profiles, rate performance, and cyclic voltammetry. In the working voltage between 3.0 and 0.01 V, LiVMoO6 delivers a high reversible capacity of more than 900 mAh g(-1) at the current density of 100 mA g(-1) and a superior rate capability with discharge capacity of ca. 584 and 285 mAh g(-1) under the high current densities of 2 and 5 A g(-1), respectively. Moreover, ex situ X-ray diffraction and X-ray photoelectron spectroscopy are utilized to examine the phase evolution and valence changes during the first lithiated process. A small amount of inserted Li(+) induces a decomposition of LiVMoO6 into Li2Mo2O7 and V2O5, which play the host during further lithiated processes. When being discharged to 0.01 V, most V(5+) change into V(3+)/V(2+), suggesting intercalation/deintercalation processes, whereas Mo(6+) are reduced into a metallic state on the basis of the conversion reaction. The insights obtained from this study will benefit the design of novel anode materials for lithium-ion batteries.