Orthorhombic MoO3 Research Articles

Effects of MoO3 crystalline structure of MoO3–SnO2 catalysts on selective oxidation of glycol dimethyl ether to 1,2-propandiol

Hexagonal, monoclinic and orthorhombic MoO3 crystalline phases were prepared to explore rational design requirements of the MoO3–SnO2 structure that are beneficial for the reaction of glycol dimethyl ether to 1,2-propandiol.

Supercapacitor based on few-layer MoO<SUB align="right">3 nanosheets prepared by solvothermal method

In this work, few-layer orthorhombic MoO3 (α-MoO3) nanosheets with high crystallinity were prepared by solvothermal method. The thickness of the prepared MoO3 nanosheets is about 15 nm. The effects of temperature and solvent on the growth and morphology of MoO3 nanosheets were investigated and the results show that temperature ranging from 140 to 180°C has little influence on the morphology and size of MoO3 nanosheets, while the kind of solvent has a great impact on it. The electrochemical performances of the prepared MoO3 nanosheets were studied by cyclic voltammetry and chronopotentiometry. The results show that the specific capacitance of the MoO3 nanosheets depends on the temperature, and the maximum specific capacitance of 136.8 F/g is obtained at 160°C.

Oxygen deficiency in MoO3 polycrystalline nanowires and nanotubes

We report on the synthesis of polycrystalline molybdenum oxide (MoO3) nanowires via oxidation of molybdenum-sulfur-iodine (Mo6S2I8) nanowires. This unique synthesis route results in an interesting morphology comprising porous nanowires and nanotubes. We found the nanowires to have the orthorhombic MoO3 structure. The structure is slightly oxygen deficient which results in the appearance of a new resonant Raman band (1004 cm−1) and paramagnetic defects (Mo5+) of both the point and crystallographic shear plane nature.

Facile synthesize α-MoO3 nanobelts with high adsorption property

A simple approach is explored to synthesize orthorhombic MoO3 (α-MoO3) nanobelts using sodium molybdate (Na2MoO4) and fluoboric acid (HBF4). In the reaction, HBF4 not only serves as a reagent to provide H+, but also a surfactant to manipulate the morphology and crystalline phase of the as-prepared products. The results show that the as-prepared samples are MoO3 nanobelts with 300nm in width, 50nm in thickness and 2–5μm in length. Moreover, the possible formation mechanism of α-MoO3 nanobelts with HBF4 is studied. Finally, devoted to the belt-like shape and high stability, the MoO3 nanobelts exhibit a good adsorption performance for methyl blue (MB).

Ion beam induced structural and electrical modifications of Fe doped molybdenum oxide thin films

In the present paper, structural and electrical properties of 2% Fe doped molybdenum oxide thin films grown by the pulsed laser deposition (PLD) technique have been reported. Ion beam induced modifications of these films were studied under the bombardment of 100MeV Ni8+ ions. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and micro-Raman measurements suggested the formation of mainly orthorhombic (α-phase) MoO3 in the films along with the presence of monoclinic (β-phase) MoO3 and MoO2. Ion bombardment induced structural disorder in the MoO3 films. Room temperature resistivity of the as-grown film was 13.85Ω-cm. The resistivity increased with increasing ion fluence (ϕ), and the values were found to be 47.6Ω-cm, 73.7Ω-cm, and 101.6Ω-cm for ϕ=1×1012, 1×1013, and 1×1014 ions-cm−2, respectively.

Vacuum Topotactic Conversion Route to Mesoporous Orthorhombic MoO3 Nanowire Bundles with Enhanced Electrochemical Performance

The growth of mesoporous bundles composed of orthorhombic MoO3 nanowires with diameters ranging from 10 to 30 nm and lengths of up to 2 μm by topotactic chemical transformation from triclinic α-MoO3·H2O nanorods under vacuum condition at 260 °C is achieved. During the process of vacuum topotactic transformation, the nanorod frameworks of the precursor α-MoO3·H2O can be preserved. The crystal structures, molecular structures, morphologies, and growth behavior of the precursory, intermediate and final products are characterized using powder X-ray diffraction (PXRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED). Detailed studies of the mechanism of the mesoporous MoO3 nanowire bundles formation indicate topotactic nucleation and oriented growth of the well-organized orthorhombic MoO3 nanowires inside the nanorod frameworks. MoO3 nanocrystals prefer [001] epitaxial growth direction of triclinic α-MoO3·H2O nanorods...

Substrate Temperature Influenced Physical and Electrochromic Properties of MoO3 Thin Films

Molybdenum oxide (MoO3) films were deposited on glass and silicon substrates by sputtering of molybdenum target at different substrate temperatures in the range 473-573 K at a constant oxygen partial pressure of 4x10-4 mbar employing RF magnetron sputtering technique. The effect of substrate temperature on structural, morphological, electrical and optical properties of the MoO3 films was systematically studied. X-ray diffraction studies revealed that the films formed at 303 K were amorphous in nature, while those deposited at substrate temperature 473 K were orthorhombic MoO3 with crystallite size of 27 nm and the crystallinity increased with increase of substrate temperature. The scanning electron micrographs of the films deposited at 303 K were of fine grain structure in amorphous back ground and the films formed at 523 K contained the grains with shape of platelets piled one over the other with size of about 1 μm. Fourier transform infrared transmittance spectra exhibited the characteristic vibration modes of MoO3. The electrical resistivity of the films decreased with increase of substrate temperature due to partial filling of oxygen ion vacancies. The optical band gap and refractive index of the films increased with the increase of substrate temperature. The MoO3 films formed at substrate temperature of 523 K exhibits high optical modulation of 22% and coloration efficiency of 30 cm2/C.

Fabrication of one-dimensional SnO2/MoO3/C nanostructure assembled of stacking SnO2 nanosheets from its heterostructure precursor and its application in lithium-ion batteries

Carbon-coated one-dimensional (1-D) SnO2/MoO3 nanostructure (SnO2/MoO3/C) composed of densely stacked SnO2 nanosheets, uniformly distributing in amorphous MoO3 matrix, is obtained from the 1-D SnO2/MoO3 heterostructure, which is prepared for the first time by a facile, one-pot hydrothermal method. The precursor 1-D SnO2/MoO3 heterostructure is composed of SnO2 nanosheets, adhering to the two edges of 1-D MoO3 nanobelt by lattice matching between the (140) plane of orthorhombic MoO3 and (110) plane of rutile SnO2. By prolonging the hydrothermal reaction time, the as-obtained 1-D SnO2/MoO3 heterostructure is converted to a novel 1-D nanostructure, amorphous MoO3 that deposits uniformly on the surface of the SnO2 nanosheets with the preservation of the front SnO2 1-D architecture. For optimizing performance, 1-D SnO2/MoO3/C nanostructure is obtained by carbon coating on the surface of the novel 1-D nanostructure MoO3/SnO2via the pyrolysis of acetylene. Because of the 1-D nanostructure composed of nanosheets and the carbon matrix, the SnO2/MoO3/C nanocomposites exhibit an outstanding high-rate cycling performance, delivering a reversible discharge capacity of more than 560 mA h g−1 after 120 cycles at a high current density of 200 mA g−1.

Fabrication and enhanced electrochemical properties of α-MoO3nanobelts using dodecylbenzenesulfonic acid as both reactant and surfactant

In this work, we introduce a simple approach to fabricate orthorhombic MoO3 (α-MoO3) nanobelts using sodium molybdate and dodecylbenzenesulfonic acid (DBSA). Importantly, DBSA not only acts as a reagent to provide H+, but also serves as a surfactant to stabilize and manipulate the morphology of the as-obtained products. The morphology, chemical composition and crystal structure of the as-prepared α-MoO3 nanobelts were systematically characterized by scanning electron microscopy, energy dispersive spectroscopy, selected area electron diffraction, X-ray diffraction, transmission electron microscopy (including high-resolution imaging), Fourier transformation infrared spectroscopy and Raman spectroscopy. The results show that the dimensions of the as-prepared α-MoO3 nanobelts are 150–350 nm in width, 50–70 nm in thickness and 1–5 μm in length. Moreover, the electrochemical properties of the samples were analyzed utilizing cyclic voltammetry (CV), chronopotentiometry (CP) and AC impedance in a 0.5 M aqueous Li2SO4 solution. These studies reveal that the maximum specific capacitance of the α-MoO3 nanobelts is much higher than those MoO3 nanomaterials in recently reported papers. Furthermore, the charge–discharge stability measurements indicate a retention of specific capacitance of about 95% after 500 continuous charge–discharge cycles at a current density of 0.25 A g−1, demonstrating that the as-prepared α-MoO3 nanobelts can serve as most excellent electrode materials for supercapacitors.

Synthesis of MoS2 and MoO3 hierarchical nanostructures using a single-source molecular precursor

MoS2 nanoflake clusters were synthesized via hydrothermal treatment of an air-stable, easily obtained single-source molecular precursor (molybdenum diethyldithiocarbamate oxide, Mo((C2H5)2NCS2)2O2) in deionized water at 200°C for 24h; and orthorhombic phase MoO3 (α-MoO3) nanoplate clusters were obtained by heating MoS2 nanoflake clusters in air at 350°C for 5h. The obtained products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and field emission scanning electronic microscopy. Besides, the comparative synthesis experiment by direct pyrolysis of ammonium peramolybdate suggested that MoS2 nanoflake clusters might play a template role in the formation of α-MoO3 nanoplate clusters.

Hydrothermal Synthesis and Ethanol-Sensing Properties of MoO<sub>3</sub> Nanobelts

Uniform MoO3 nanobelts were synthesized through a fast and simple hydrothermal route without any other agents. The hydrothermal reaction was performed at 180 °C for 12 h using a HNO3 aqueous solution as the solvent. The phases and microstructures were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the sample obtained was an orthorhombic MoO3 phase, and had a belt-like morphology with lengths of 510 μm and apparent widths of about 220 nm. The MoO3 nanobelts obtained were used as the sensing materials to fabricate chemical sensors for detection of some volatile organic compounds (VOCs) (including ethanol, methanol, isopropanol, acetone, methanal, and benzene). The gas-sensing results indicated that the sensor of the α-MoO3 nanobelts has enhanced ethanol-sensing performance, e.g., with the highest sensitivity of Sr =144 for 500 ppm ethanol vapor operating at 300 °C.

Preparation and characterization of α-MoO3 nanobelt and its application in supercapacitor

In this work, we introduce a simple approach to synthesize orthorhombic MoO3 (α-MoO3) nanobelts with dichloromethane (CH2Cl2). More importantly, dichloromethane acts as a reagent to slowly provide H+ through hydrolysis, which facilitates to manipulate the morphology of the as-obtained products. The electrochemical properties of the samples were analyzed using cyclic voltammetry and chronopotentiometry. The results show that the maximum specific capacitance of the α-MoO3 nanobelts is much higher than those of MoO3 nanoplates with 280Fg−1, MoO3 nanowires with 110Fg−1 and MoO3 nanorods with 30Fg−1. Furthermore, the charge–discharge stability measurements indicate a retention of specific capacitance of about 90% after 500 cycles at a current density of 0.25Ag−1, demonstrating that the α-MoO3 nanobelts can serve as excellent electrode materials for supercapacitors.

‘Li’ doping induced physicochemical property modifications of MoO3 thin films

Undoped and lithium (Li) (1–5wt%) doped MoO3 thin films were deposited over ITO coated glass substrates by spray pyrolysis at a substrate temperature of 325°C. Undoped film was oriented along the 〈0k0〉 direction. The texture coefficient value of the undoped film was higher for the (020) plane compared to other planes of undoped and ‘Li’ doped films. The 100% peak (021) plane of orthorhombic MoO3 and hexagonal phase were induced upon doping with ‘Li’. The crystallite size of the undoped film is less compared to the ‘Li’ doped films. The intense Raman peak at 996cm−1 is due to the terminal oxygen (Mo6+=O stretching mode) in the orthorhombic α-MoO3 phase. The characteristic Mo 3d5/2 and 3d3/2 doublet caused by spin–orbit coupling are clearly resolved with a splitting of 3.1eV in the XPS spectra. Scanning electron microscope (SEM) image shows a change in the microstructure, consistent with the change from α-MoO3 to mixed α and hexagonal phases. Sprout like features were observed in SEM image and rod like features in atomic force microscope (AFM) images. Both direct and indirect band gap showed red shift upon doping with ‘Li’ compared to undoped film as estimated from the transmittance spectra. Intensity of the green photoluminescence (PL) emission spectra was found to quench with ‘Li’ concentration. Cyclic voltammetry result shows that the presence of mixed phases in ‘Li’ doped films decreases the electrochemical performance. Transport study reveals that the carrier concentration and mobility of the ‘Li’ doped films are lower compared to the undoped film which is due to the evolution of hexagonal phase upon doping with ‘Li’. A dye sensitized solar cell (DSSC) was fabricated using undoped MoO3 film as photoanode and its efficiency is calculated.

Orthorhombic MoO3 Nanofibers as Cathode Materials for Lithium Batteries

We report the structural and electrochemical properties of MoO3 nanofibers synthesized by hydrothermal reaction from acidified ammonium heptamolybdate tetrahydrate precursor. Structural analysis shows that MoO3 nanofibers 50-80 nm in diameter and a several micrometers in length are grown in the orthorhombic system (Pbnm S.G.). The composition MoO2.9975 was determined by Rietveld refinement and magnetic susceptibility measurements. The electrochemical performance of Li//MoO3 cells with nanofibers deliver a better discharge capacity after 40 cycles than MoO3 bulk.

Hydrothermal synthesis of MoO3 micro-belts

AbstractIn this paper we report the synthesis of molybdenum trioxide (MoO3) microstructures via acidification of sodium molybdate (Na2MoO4). The structure and morphology of the products were characterized by means of X-ray powder diffraction, Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. It is found that as-synthesized micro-belts were pure orthorhombic structured MoO3 grown along [010], with length up to more than 10 μm and width ranging from 200 to 500 nm. On the basis of the experimental facts, a mechanism for the growth of the MoO3 belts is proposed.

Orthorhombic MoO3 Nanofibers as Cathode Materials for Lithium Batteries

Orthorhombic MoO3 Nanofibers as Cathode Materials for Lithium Batteries

Orthorhombic MoO3 Nanofibers as Cathode Materials for Li Batteries

not Available.

Hydrothermal synthesis and electrochemical properties of α-MoO3 nanobelts used as cathode materials for Li-ion batteries

Uniform α-MoO3 nanobelts were successfully synthesized by the hydrothermal process at 180°C for 20 h of the acidic solutions with different pH values of 0–0.75, adjusted using HCl (conc.). XRD and SEM results revealed that the pH of the precursor solutions played an important role in the phase, impurities, and morphology of the products. At the pH=0, the perfect α-MoO3 nanobelts with a few tens of microns long were synthesized. By the TEM characterization, orthorhombic MoO3 has a distinctive layered structure along the [010] direction, consisting of distorted MoO6 octahedrons connected by common corners along the [100] direction and common edges along the [001] direction. The electrochemical measurement showed that the α-MoO3 nanobelts have high specific charge capacity.

Electron beam-induced structural transformations of MoO3 and MoO3−x crystalline nanostructures

Electron beam-induced damage and structural changes in MoO3 and MoO3−x single crystalline nanostructures were revealed by in situ transmission electron microscopy (TEM) examination (at 200 kV) after few minutes of concentrating the electron beam onto small areas (diameters between 25 and 200 nm) of the samples. The damage was evaluated recording TEM images, while the structural changes were revealed acquiring selected area electron diffraction patterns and high resolution transmission electron microscopy (HRTEM) images after different irradiation times. The as-received nanostructures of orthorhombic MoO3 were transformed to a Magneli’s phase of the oxide (γ-Mo4O11) after ~10 min of electron beam irradiation. The oxygen loss from the oxide promoted structural changes. HRTEM observations showed that, in the first stage of the reduction, oxygen vacancies generated by the electron beam are accommodated by forming crystallographic shear planes. At a later stage of the reduction process, a polycrystalline structure was developed with highly oxygen-deficient grains. The structural changes can be attributed to the local heating of the irradiated zone combined with radiolysis.

In Situ Raman Spectroscopy of H2 Gas Interaction with Layered MoO3

It is known that the unique layered structure of orthorhombic MoO3 (α-MoO3) facilitates the interaction with H2 gas molecules and that the surface-to-volume ratios of the crystallites play an important role in the process. MoO3 was deposited on a wide variety of transparent substrates using thermal evaporation in order to alter the surface-to-volume ratios of the crystallites. In situ Raman spectroscopy was employed to investigate the interaction between MoO3 and 1% H2 in both N2 and synthetic air environments, while incorporating Pd as a catalyst at room temperature. This study confirmed that the layered MoO3 with a high surface-to-volume ratio facilitated the H2 gas interaction. The Raman spectroscopy studies revealed that the H+ ions mainly interacted with the doubly coordinated oxygen atoms and caused the crystal transformation from the original α-MoO3 into the mixed structure of hydrogen molybdenum bronze and substoichiometric MoO3, eventually forming oxygen vacancies and water. It was also found tha...