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a FT-IR, b Raman, and c UV-Vis absorption spectra with d plots of (αhν)² as a function of energy E for both α-MoO3 nanobelts and h-MoO3 microrods
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Two modifications of molybdenum trioxide with orthorhombic (α-MoO3) and hexagonal (h-MoO3) crystal structure have been synthesized by a microwave-assisted hydrothermal method, facilitated by formic acid. Characterization by means of X-ray diffraction, scanning electron microscopy, specific surface analysis, and Fourier-transform infrared, Raman, an...
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... Very few reports are available on the synthesis of single crystal strip-like structure of orthorhombic MoO 3 sample [1,16]. There are various methods are available for the synthesis of single crystal a-MoO 3 like ultrasonicassisted [17] hydrothermal [18] spray pyrolysis [19] chemical co-precipitation [20], microwave technique [21], combustion route [22] etc. From these reported methods microwave and co-precipitation method combinly used for the synthesis of a-MoO 3 micro-strips hence called as microwave-assisted chemical co-precipitation method. Microwaves synthesis is rapid method due to its high power densities, fast efficient production which reduces production cost. ...
The orthorhombic MoO3 micro-strips sample was synthesized using microwave assisted chemical co-precipitation technique. Synchrotron X-ray Diffraction (SXRD) pattern and Rietveld Refinement was used to estimate structural parameter, crystallite size of sample. It reveals that the synthesized sample MoO3 crystallized as an orthorhombic phase. X-ray Absorption Spectroscopy (XAS) measurement, which comprises both X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques, have been carried out on Mo K-edge to probe the local structure of samples. Local structure is also confirmed from the SXRD and Raman spectra of sample. XAS measurement reveals that the first bond length of Mo-O and Mo-Mo is 1.69 and 3.42 Å in orthorhombic MoO3 respectively. Transmission electron microscopy and SAED patterns showed stripe-like structure and single-crystal formation of MoO3 respectively.
... This may be due to the dielectric relaxation phenomena occurring in the compound [41]. The tangent loss (tanδ) caused by the dipole relaxation phenomena decreases with frequency, as seen in the tanδ frequency plots [42]. which it goes to a lower value. ...
... This may be due to the dielectric relaxation phenomena occurring in the compound [41]. The tangent loss (tanδ) caused by the dipole relaxation phenomena decreases with frequency, as seen in the tanδ frequency plots [42]. ...
In the present work, pure and Cr-doped MoO3 microrods were successfully prepared through the sol gel auto combustion method. The phase evaluation and microstructural, dielectric, and optical properties of synthesized samples were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and an impedance analyzer (1 MHz–3 GHz). All the samples showed hexagonal structure with space group (P63). According to Vegard’s law, lattice parameters increase with the increase in chromium (Cr3+) contents. In addition, the Williamson–Hall (W–H) plot was drawn for evaluating the micro-strain (εW-H) and crystallite size (DW-H) parameters. From microstructural analysis it was found that the size of microrods increased along with Cr3+ contents. Decreasing band gap energy was observed (from 2.98 to 2.71 eV) with increasing Cr3+ contents. The variation of the dielectric constant and tangent loss of MoO3 microrods with respect to frequency were analyzed.
... The sharp absorption edge at 420 nm indicates the visible light absorption. The absorption at this region arises due to the electronic transition from the higher valance band (HOMO level) containing of O 2p orbital hybridized with Mo 4d to the lower conduction band which is composed of Mo 4d (LUMO level) orbital hybridized with O 2p [22]. Kubelka-Munk (K-M) function was employed to estimate the band gap energies of the NPs [23], ...
In this work, we herein report the synthesis of pure and Mn doped MoO3 (NPs) by hydrothermal method. The crystal structure as well as phase purity of both the pure and Mn doped MoO3 NPs were investigated by using XRD studies. The average crystallite sizes for the NPs were found to exist in the range of 27-17 nm. The surface morphologies and elemental composition of the NPs were examined using SEM, HRTEM and EDX analysis. The vibrational spectral studies of the NPs revealed the characteristic vibrational assignments with reference to the existing structural data. The optical band gap energies of the samples obtained using Kubelka-Munk function were observed to be in the range of 2.77-2.68 eV. The XPS spectra of the NPs were studied to confirm the oxidation state of Mn ions. The magnetic studies reveal the ferromagnetic nature in Mn doped MoO3 NPs making them a promising candidate suitable for spintronic applications.
... Current knowledge concerning the synthesis of a hexagonal structure of MoO3 via the microwave method is not yet sufficient. However, Zakharova et al. [40] reported on electrochemical studies of αand h-MoO3 synthesized via a microwave-assisted hydrothermal method. Therefore, the obtaining of well-formed crystalline forms of anatase and h-MoO3 is an additional novelty of this work. ...
Hydrothermal crystallization was used to synthesize an advanced hybrid system containing titania and molybdenum disulfide (with a TiO2:MoS2 molar ratio of 1:1). The way in which the conditions of hydrothermal treatment (180 and 200 °C) and thermal treatment (500 °C) affect the physicochemical properties of the products was determined. A physicochemical analysis of the fabricated materials included the determination of the microstructure and morphology (scanning and transmission electron microscopy—SEM and TEM), crystalline structure (X-ray diffraction method—XRD), chemical surface composition (energy dispersive X-ray spectroscopy—EDS) and parameters of the porous structure (low-temperature N2 sorption), as well as the chemical surface concentration (X-ray photoelectron spectroscop—XPS). It is well known that lithium-ion batteries (LIBs) represent a renewable energy source and a type of energy storage device. The increased demand for energy means that new materials with higher energy and power densities continue to be the subject of investigation. The objective of this research was to obtain a new electrode (anode) component characterized by high work efficiency and good electrochemical properties. The synthesized TiO2-MoS2 material exhibited much better electrochemical stability than pure MoS2 (commercial), but with a specific capacity ca. 630 mAh/g at a current density of 100 mA/g.
... 28,29 The narrow band located at 992 cm −1 is related to asymmetric stretching of the oxygen atoms (MoO) in the α-MoO 3 phase. 30 The intense band appearing at 817 cm −1 is assigned to the Mo-O-Mo symmetric stretching vibrations (or the doubly connected bridge-oxygen Mo-O-Mo), while asymmetric stretching of the triply connected bridge-oxygen Mo 3 -O along the c-axis can be found at 663 cm −1 . 31 Both XRD and Raman results showed the success in obtaining single phase orthorhombic α-MoO 3 structures. ...
The synthesis of α-MoO3 nanoplates with unique well-faceted rectangular morphology produced by a polymeric solution route is presented in this work. This versatile chemical route allowed the growth of layered nanoplates on different crystalline substrates to manufacture electronic/optoelectronic nanodevices. The α-MoO3 crystalline phase was identified by both X-ray diffraction (XRD) and Raman spectroscopy. Scanning electron (SEM) and atomic force (AFM) microscopies showed that the well-faceted rectangular layered nanoplates can be obtained depending on a fine control of the synthesis parameters due to the MoO3 sublimation. Gas sensing measurements revealed that the α-MoO3 nanoplates exhibit enhanced response to NO2, with sensor signals up to 50, combined with a low optimum operating temperature. In addition, the devices exhibited highest selectivity to NO2 relative to H2, CO and CH4, which can be a consequence of the specific exposed surface plane. These results reveal that layered α-MoO3 nanoplates are a promising material for use in the manufacturing of high-performance NO2 gas sensor nanodevices.
... Current knowledge concerning the synthesis of a hexagonal structure of MoO3 via the microwave method is not yet sufficient. However, Zakharova et al. [40] reported on electrochemical studies of αand h-MoO3 synthesized via a microwave-assisted hydrothermal method. Therefore, the obtaining of well-formed crystalline forms of anatase and h-MoO3 is an additional novelty of this work. ...
TiO2-MoO3 composite systems were successfully prepared using a template-assisted microwave method at molar ratios TiO2:MoO3 = 8:2, 5:5 and 2:8. The synthesized material systems were comprehensively characterized, in terms of their crystalline structure (XRD and Raman spectroscopy), morphology (SEM, TEM and HRTEM analysis) and parameters of the porous structure (low-temperature N2 sorption). The materials exhibited highly crystalline phases: anatase and hexagonal molybdenum trioxide. Moreover, TEM analysis revealed hexagonal prism particles of MoO3 and nanocrystalline particles of TiO2. The proposed template-assisted microwave synthesis enabled the incorporation of TiO2 particles on the surface of hexagonal particles of MoO3, which resulted in a stable junction between titania and molybdenum trioxide. The values of BET surface area were 57, 29 and 11 m2/g for samples obtained at molar ratios TiO2:MoO3 = 8:2, 5:5 and 2:8 respectively. In electrochemical applications, titanium dioxide plays a crucial role as an intercalation intensifier, in which MoO3 is responsible for current conduction. Taking account of the potential electrochemical applications, the best system was obtained at the molar ratio TiO2:MoO3 = 5:5. The anode could maintain a capacity of 400 mAh/g at current densities in the range 100–1000 mA/g at potential values ranging from 1.00 to 3.30 V vs. Li/Li+. X-ray photoelectron spectroscopy (XPS) confirmed the effective intercalation of lithium ions into the TiO2-MoO3 composite materials.
Ni–Mo–SrSO4 composites with different Mo amount were prepared by hot pressing in a vacuum. The oxygen-deficient environment derived from the degradation of SrSO4 during fabrication process led to the formation of SrMoO4, Sr2NiMoO6, and SrO in the sintered composites. With the increment in the contents of Mo, excessive dissolved Mo atoms accelerated the oxidation of Ni in the oxygen-deficient environment, which eradicated SrMoO4 phase. As compared to sintered material containing Sr2NiMoO6 and SrO, the appearance of SrMoO4 led to a distinct decrease in the density and microhardness. To reveal the effect of SrMoO4 on the wear mechanism, the tribological properties of the sintered composites against Al2O3 ball were investigated at different temperatures. The result indicated that the in-situ composite consisting of 80.75 wt.% Ni, 14.25 wt.% Mo, and 5 wt.% SrSO4 exhibited good friction and wear properties at room temperature (RT) and 800 °C, which was attributed to the development of the intact tribofilm with grooves consisting of SrMoO4, Sr2NiMoO6, NiO, and h-MoO3 at RT and the synergistic lubricating effect of SrMoO4, Sr2NiMoO6, and oxides (NiO, α-MoO3, SrMoO4, α-NiMoO4, and β-NiMoO4) at 800 °C.
Orthorhombic molybdenum trioxide (α-MoO3) electrode material experiences severe capacity fading and poor cycling stability in aqueous electrolytes. We investigated the charge-storage performance of α-MoO3 electrode in aluminium trifluoromethanesulfonate (Al(OTf)3)-based salt-in-water electrolyte (SiWE) and water-in-salt electrolyte (WiSE). It was found that α-MoO3 electrode exhibits significantly different cycling stabilities in both electrolytes with capacity retentions of 8% using the former and 87% using the latter. This is because α-MoO3 electrode maintains its crystal structure upon cycling in WiSE, but experiences substantial structural collapses and partial dissolution upon cycling in SiWE. This behaviour was inferred from both operando electrogravimetry and ex situ analyses. Research results suggest that the predominant charge-storage mechanism in α-MoO3 electrode using WiSE is the intercalation of protons due to electrolyte hydrolysis with some contribution from surface pseudocapacitance enabled by Al³⁺ ions. A two-volt full cell fabricated from α-MoO3 electrode as anode and copper hexacyanoferrate (CuHCF) electrode as cathode using WiSE delivers volumetric and gravimetric energies of 10.4 Wh/L and 26.5 Wh/kg, respectively, with 78% capacity retention after 2500 cycles. This study provides an insightful understanding of the electrochemical performance of α-MoO3 electrode in Al(OTf)3-based electrolytes.
