Oxidation State Of Molybdenum Research Articles

Fractal supported electrochemical analysis of MoO3 decorated AlOOH binary composite for supercapacitor application

The AlOOH/MoO3 binary composite electrodes are synthesized by layer-by-layer method to enhance the supercapacitive property of AlOOH by taking advantage of multiple oxidation states of molybdenum. The X-ray diffraction characterization reveals the polycrystalline nature of nanocomposite. The elements and their chemical states are analysed using X-ray photoelectron spectroscopy. The binary composite exhibits interconnected network-like morphology resembling a fractal nature. The three-electrode measurement in 1 M KOH electrolyte shows the highest specific capacity (Cs) of 1638.15 C g-1@ 5 mV s-1 for binary composite, which is greater than the capacity of individual components. Also, we get Cs of 1124.41 C g-1 for 10 cycle MoO3 while its theoretical capacity is 1005 C g-1. The excellent electrochemical performance is a consequence of multiple redox active sites present in the nanocomposite, lower resistance, porous interconnected network-like structure, and shorter relaxation time. The synergy of AlOOH with MoO3 enhances its charge storage capacity. The obtained electrochemical results are also theoretically supported by fractal analysis. Among all the electrodes, the 10 cycle AlOOH/MoO3 nanocomposite displays high value of fractal dimension, which is advantageous for supercapacitor application. Furthermore, we have fabricated a symmetric supercapacitor device to understand the practicality of current work. The fabricated device displays Cs of 68.41 F g-1 within 1.6 V potential window with ∼71 % capacity retention and 100 % coulombic efficiency after 7000 charge-discharge cycles. The highest energy density of 24.32 Wh kg-1 is achieved for the power density of 3907 W kg-1.

Gamma rays impact on 2D-MoS2 in water solution.

Two-dimensional transition metal dichalcogenides, particularly MoS2, are interesting materials for many applications in aerospace research, radiation therapy and bioscience more in general. Since in many of these applications MoS2-based nanomaterials can be placed in an aqueous environment while exposed to ionizing radiation, both experimental and theoretical studies of their behaviour under these conditions is particularly interesting. Here, we study the effects of tiny imparted doses of 511keV photons to MoS2 nanoflakes in water solution. To the best of our knowledge, this is the first study in which ionizing radiation on 2D-MoS2 occurs in water. Interestingly, we find that, in addition to the direct interaction between high-energy photons and nanoflakes, reactive chemical species, generated by γ-photons induced radiolysis of water, come into play a relevant role. A radiation transport Monte Carlo simulation allowed determining the elements driving the morphological and spectroscopical changes of 2D-MoS2, experimentally monitored by SEM microscopy, DLS, Raman and UV-vis spectroscopy, AFM, and X-ray photoelectron techniques. Our study demonstrates that radiolysis products affect the Molybdenum oxidation state, which is massively changed from the stable + 4 and + 6 states into the rarer and more unstable + 5. These findings will be relevant for radiation-based therapies and diagnostics in patients that are assuming drugs or contrast agents containing 2D-MoS2 and for aerospace biomedical applications of 2DMs investigating their actions into living organisms on space station or satellites.

Dual‐mode sensing biopolymer membrane impregnated with molybdenum for ethylene detection and monitoring of fruits

AbstractIn this study, a dual‐mode sensing biopolymer membrane employing chitosan (CS), polyvinyl alcohol (PVA), and ammonium molybdate (AM) was developed for optical and electrochemical detection of ethylene. The biopolymer composite was characterized by X‐ray diffraction (XRD), Fourier transform infra‐red (FTIR), and scanning electron microscopy (SEM).The relationship between ethylene concentration and optical/electrochemical response was investigated. XRD analysis showed enhanced ionic conduction, supported by SEM images showing uniform pore distribution within the synthesized membrane, facilitating effective gas interaction with Molybdenum. The increased FTIR peak intensities with higher amount of molybdenum in the membrane indicates enhanced molecular interactions. Applied to a microelectrode chip, the membrane exhibits a measurable electrochemical response with oxidation peak appearing in cyclic voltammogram as Molybdenum ions undergo reduction upon ethylene exposure. Colorimetric measurements, based on CIELAB values, reveals visible color shift with increasing ethylene concentrations, particularly at 10% molybdenum impregnation. Ionic conductivity and total color difference exhibit parallel variation with ethylene concentrations. X‐ray photoelectron spectroscopy confirms molybdenum oxidation state shift from +6 to +5 in the membrane upon ethylene interaction. The inexpensive colorimetric method enables direct color change visualization in practical applications. The resulting dual‐functional biopolymer membrane shows adaptability and versatility by responding to both optical and electrochemical signals.

Luminescent and Photoredox‐Active Molybdenum(0) Complexes Competitive with Isoelectronic Ruthenium(II) Polypyridines

AbstractRuthenium(II) complexes with chelating polypyridine ligands are among the most frequently investigated compounds in photophysics and photochemistry, owing to their favorable luminescence and photoredox properties. Equally good photoluminescence performance and attractive photocatalytic behavior is now achievable with isoelectronic molybdenum(0) complexes. The zero‐valent oxidation state of molybdenum is stabilized by carbonyl or isocyanide ligands, and metal‐to‐ligand charge transfer (MLCT) excited states analogous to those in ruthenium(II) complexes can be established. Microsecond MLCT excited‐state lifetimes and photoluminescence quantum yields up to 0.2 have been achieved in solution at room temperature, and the emission wavelength has become tunable over a large range. The molybdenum(0) complexes are stronger photoreductants than ruthenium(II) polypyridines and can therefore perform more challenging chemical reductions. The triplet nature of their luminescent MLCT states allows sensitization of photon upconversion via triplet‐triplet annihilation, to convert low‐energy input radiation into higher‐energy output fluorescence. This review summarizes the current state of the art concerning luminescent molybdenum(0) complexes and highlights their application potential. Molybdenum is roughly 140 times more abundant and far cheaper than ruthenium, hence this research is relevant in the greater context of finding more sustainable alternatives to using precious and rare transition metals in photophysics and photochemistry.

Luminescent and Photoredox-Active Molybdenum(0) Complexes Competitive with Isoelectronic Ruthenium(II) Polypyridines.

Ruthenium(II) complexes with chelating polypyridine ligands are among the most frequently investigated compounds in photophysics and photochemistry, owing to their favorable luminescence and photoredox properties. Equally good photoluminescence performance and attractive photocatalytic behavior is now achievable with isoelectronic molybdenum(0) complexes. The zero-valent oxidation state of molybdenum is stabilized by carbonyl or isocyanide ligands, and metal-to-ligand charge transfer (MLCT) excited states analogous to those in ruthenium(II) complexes can be established. Microsecond MLCT excited-state lifetimes and photoluminescence quantum yields up to 0.2 have been achieved in solution at room temperature, and the emission wavelength has become tunable over a large range. The molybdenum(0) complexes are stronger photoreductants than ruthenium(II) polypyridines and can therefore perform more challenging chemical reductions. The triplet nature of their luminescent MLCT states allows sensitization of photon upconversion via triplet-triplet annihilation, to convert low-energy input radiation into higher-energy output fluorescence. This review summarizes the current state of the art concerning luminescent molybdenum(0) complexes and highlights their application potential. Molybdenum is roughly 140 times more abundant and far cheaper than ruthenium, hence this research is relevant in the greater context of finding more sustainable alternatives to using precious and rare transition metals in photophysics and photochemistry.

Facile hydrothermal synthesis of MoS2 nano-worms-based aggregate as electrode material for high energy density asymmetric supercapacitor

Nowadays, supercapacitors and batteries are trending electrochemical energy storage devices. However, their low energy density and uncertain power density limited their applications, respectively. Recently, the latest innovation in energy storage devices, called hybrid supercapacitors, has appeared as an eventual energy storage device that demonstrates a hybrid storage mechanism of both supercapacitors and batteries. In this work, MoS2 has been prepared by the facile hydrothermal method, characterized by different techniques, and applied as an electrode in supercapacitors and supercapatteries. The XRD patterns and EDX confirm the successful synthesis of MoS2 with an average crystallite size of 62.25 nm, while the SEM images show the randomly oriented nanoworms of MoS2. The XPS spectrum depicts the presence of variable oxidation states of molybdenum (Mo4+and Mo6+) in the MoS2. The electrochemical performance shows that the highest specific capacitance and specific capacity reached 1866.66 F/g and 1119.99 C/g, respectively, at a scan rate of 5 mV/s for MoS2. The asymmetric supercapacitor device is made from (Graphite/MoS2) using as a working electrode and activated carbon as a cathode, which are separated by filter paper. Furthermore, the Dunn's model is utilized to evaluate of capacitive and battery mechanisms and shows the dominant role of diffusive and surface-controlled developments at low and high scan rates, respectively, owing to the change in diffusion time of electrolyte species. The fabricated device shows an energy density and power density of 103.51 Wh/kg and 3807.59 W/kg at a current density of 1 and 7 A/g, respectively, with 93.52% capacity stability and 99.8% coulombic efficiency. This excellent performance of MoS2 is believed to be a potential electrode candidate for asymmetric supercapacitor applications.

Create Rich Oxygen Defects of Unique Tubular Hierarchical Molybdenum Dioxide to Modulate Electron Transfer Rate for Superior High‐Energy Metal‐Ion Hybrid Capacitor

Metal‐ion capacitors could merit advantages from both batteries and capacitors, but they need to overcome the severe restrictions from their sluggish reaction kinetics of the battery type electrode and low specific capacitance of capacitor type electrode for both high energy and power density. Herein, we use the Kirkendall effect for the first time to synthesize unique tubular hierarchical molybdenum dioxide with encapsulated nitrogen‐doped carbon sheets while in situ realizing phosphorus‐doping to create rich oxygen vacancies (P‐MoO2‐x@NP‐C) as a sodium‐ion electrode. Experimental and theoretical analysis confirm that the P‐doping introduced oxygen defects can partially convert the high‐bond‐energy Mo–O to low‐bond‐energy Mo–P, resulting in a low oxidation state of molybdenum for enhanced surface reactivity and rapid reaction kinetics. The as‐prepared P‐MoO2‐x@NP‐C as an ion‐battery electrode is further used to pair active N‐doped carbon nanosheet (N‐C‐A) electrode for Na‐ion hybrid capacitor, delivering excellent performance with an energy density of 140.3 Wh kg−1, a power density of 188.5 W kg−1 and long stable life in non‐aqueous solution, which ranks the best among all reported MoOx‐based hybrid capacitors. P‐MoO2‐x@NP‐C is also used to fabricate a zinc‐ion hybrid capacitor, also accomplishing a remarkable energy density of 43.8 Wh kg−1, a power density of 93.9 W kg−1, and a long stable life@2A g−1 of 32 000 cycles in aqueous solutions, solidly verifying its universal significance. This work not only demonstrates an innovative approach to synthesize high‐performance metal ion hybrid capacitor materials but also reveals certain scientific insights into electron transfer enhancement mechanisms.

Modulation of Molybdenum oxidation state via Catalytic-oxidation

Molybdenum (Mo) is a promising metal contact material to replace tungsten due to its low electrical resistivity in sub-3 nm next-generation semiconductor processes. However, the high dissolution rate of Mo during the chemical mechanical planarization (CMP) process limits its practical introduction because it deteriorates surface flatness and consequently causes decisive device failure. Herein, we report a strategy to suppress Mo dissolution by manipulating the oxidation state of Mo film via catalytic-oxidation reaction. Adoption of Fe catalyst under the trace amounts of H2O2 enables the formation of insoluble MoO2 and Mo2O5 phases while minimizing the generation of the soluble MoO3 phase. The dissolution behaviors of Mo at various oxidation states were investigated according to both oxidizer and catalyst concentrations during the CMP process. To identify the detailed dissolution phenomena of Mo, the Gibbs free energies and dissolution kinetics in different Mo oxide phases were validated using density functional theory (DFT) calculation. We successfully confirmed that catalytic-oxidation using Fe ions achieved an enhanced removal rate from 780 to 1500 Å/min, even though the dissolution rate was minimized from 636 to 57 Å/min compared to a single oxidation reaction. We believe that our results, supported by theoretical considerations and experimental results, can elucidate Mo oxidation and dissolution phenomena for application to the advanced semiconductor manufacturing processes.

Exploring the effect of oxygen environment on the Mo/CdTe/CdSe solar cell substrate configuration

Incorporating Se element into Cadmium telluride (CdTe)-based superstrate configuration solar cells have advanced impressively. However, molybdenum (Mo)/CdTe/CdSe substrate configuration devices remain relatively unexplored, and Mo foil oxidation behavior during the fabrication process is kept in the dark. This work investigates a fresh CdTe/CdSe substrate configuration solar cell using Mo substrates. Mo/CdTe/CdSe/ZnO/AZO/ITO solar cells have been fabricated, CdTe absorber layer was obtained by closed space sublimation (CSS) under ∼2000 pa pressure in varying Ar/O2 flu ratio. The champion device had an efficiency of 3.87% with unintentional Cu-doping and back contact. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-Ray spectroscopy (EDS) were applied to study the properties of CdTe films. Before CdTe deposition, molybdenum oxide (MoOx) was generated while heating the Mo substrate in an oxygen-containing environment. This buffer layer plays a pivotal role in blocking non-Ohmic back contact analyzed by current-voltage-temperature (J-V-T) measurements. Molybdenum oxidation states were extensively studied to build the relationship with a solar cell device. Our findings indicated that different oxygen partial pressure had less relevance with the CdTe surface chemical environment but was incredibly relevant for Mo metal foil oxidation states.

Molybdenum Oxide/Dopamine-Derived Carbon Electrodes with Enhanced Electrochemical Activity in Energy Storage Systems

Herein, a versatile sol-gel reaction produces new electrode materials consisting of tightly integrated molybdenum oxide and carbon derived from chemically incorporated dopamine molecules, and the materials show enhanced electrochemical activity in nonaqueous Li-ion and aqueous Zn-ion energy storage systems. The novel synthesis entails the oxidation of molybdenum in aqueous solutions of excess and limited dopamine (Dopa) hydrochloride via a hydrogen peroxide-initiated process.The transformation of molybdenum under the condition of Dopa excess (Mo:Dopa molar ratio of 1:1) resulted in the formation of a metastable precipitate of polydopamine (PDopa) spheres encapsulated by Dopa-preintercalated molybdenum oxide, (Dopa)xMoOy@PDopa. Hydrothermal treatment (HT) of (Dopa)xMoOy@PDopa precursor was concomitant with concurrent Dopa carbonization and molybdenum reduction processes, resulting in a formation of spherical matrices of Dopa-derived carbon decorated by MoO2 nanoplatelets (HT-MoO2/C), as determined through FTIR spectroscopy, Raman spectroscopy, and SEM imaging. Annealing (An) of HT-MoO2/C at 600°C under argon atmosphere (AnHT-MoO2/C) led not only to improvements in MoO2 crystallinity, but also to an increased oxidation state of molybdenum and a facilitated interaction between molybdenum-based and Dopa-derived components, resulting in an intimate MoO2/C heterointerface. Consequently, while both HT-MoO2/C and AnHT-MoO2/C showed reversible intercalation-type behavior when evaluated as electrodes versus Li/Li+ in nonaqueous lithium-ion cells, AnHT-MoO2/C demonstrated higher capacities, enhanced capacity retention, better rate capability, and lower charge transfer resistance. The AnHT-MoO2/C electrode showed an initial specific capacity of 260 mAh/g and 67% capacity retention after 50 cycles at 10 mA/g, compared to an initial specific capacity of 235 mAh/g and 47% capacity retention shown by HT-MoO2/C at the same current density. Furthermore, in rate capability experiments, HT-MoO2/C and AnHT-MoO2/C delivered specific capacities of 93 mAh/g and 120 mAh/g respectively at 100 mA/g.When molybdenum was transformed in the presence of Dopa deficit (Mo:Dopa molar ratio of 5:1), a (Dopa)xMoOy powder precursor was isolated, and subsequent hydrothermal treatment of this precursor produced an MoO3 material with carbonized Dopa molecules, HT-MoO3/C. Reference α-MoO3 electrodes (α-MoO3-ref) were synthesized similarly but in the absence of Dopa molecules in the initial sol-gel reaction. The appearance of characteristic D and G bands in the Raman spectra and distinct vibrational modes in the FTIR spectra of HT-MoO3/C confirmed the presence of carbon in its structure. SEM images showed a uniform nanobelt morphology with fragmentation due to interactions between interlayer Dopa and MoO3 layers under the conditions of hydrothermal treatment. HT-MoO3/C delivered a second-cycle capacitance of 141.4 F/g when cycled at 2 mV/s in a -0.25–0.70 V versus Ag/AgCl potential window in 5M ZnCl2 electrolyte, while α-MoO3-ref delivered a nearly two-fold smaller second-cycle capacitance of 76.1 F/g under the same conditions. HT-MoO3/C also showed increased capacitance compared to α-MoO3-ref when cycled at increasing sweep rates up to 20 mV/s. The superior performance of HT-MoO3/C prompted a study of the electrode in an expanded potential window, based on previous reports in which MoO3 showed electrochemical activity at negative potentials versus Ag/AgCl. The HT-MoO3/C electrode exhibited a capacitance of 347.6 F/g on the second cycle when cycled between -0.85–1.00V versus Ag/AgCl at 2 mV/s in 5M ZnCl2 electrolyte.This work demonstrates a new strategy to improve the electrochemical performance of transition metal oxide electrodes for next-generation energy storage systems. Integration of oxides with carbon through the wet chemistry synthesis approaches that involve carbonization of organic molecules can be used to control oxide crystal phase and heterointerfaces leading to improved charge transfer and energy storage properties.

Influence of Oxygen Dopants on the HER Catalytic Activity of Electrodeposited MoOxSy Electrocatalysts

Amorphous, polymeric molybdenum sulfide has attracted significant attention as a non-platinum group electrocatalyst for the hydrogen evolution reaction (HER). To elucidate the influence of oxygen incorporation on molybdenum sulfide catalysts, MoOxSy electrocatalysts were synthesized via a potentiostatic electrodeposition method. The presence of oxygen and the associated molybdenum oxidation state were modified by postsynthesis treatments of air exposure, annealing in an inert atmosphere, and annealing in a sulfur flux. The as deposited sample exhibited the best performance, requiring only 171 mV to reach a cathodic current density of 10 mA/cm2. While the modified films exhibited worse HER performance compared to the as deposited sample, by utilizing extensive X-ray photoelectron spectroscopy studies, we highlighted the importance of the Mo5+ oxidation state while identifying a previously unreported state within MoOxSy catalysts between Mo4+ and Mo5+.

Exploring catalyst dynamics in a fixed bed reactor by correlative operando spatially-resolved structure-activity profiling

Efficient and sustainable optimization of heterogeneous catalytic processes requires a deep understanding of catalyst structure-activity relationships that occur inside catalytic reactors in space and time. Here we introduce a catalytic profile reactor capable of simultaneously measuring spatially-resolved temperature, concentration, and X-ray absorption spectroscopy (XAS) profiles through a catalytic fixed bed. Using the oxidative dehydrogenation of ethane to ethylene over MoO3/γ-Al2O3 as a test reaction, we obtained a detailed picture of local catalyst structure and activity under realistic and well-defined reaction conditions. Concentration, temperature and XAS profiles were measured up to and beyond the point of complete O2 consumption showing a distinct transition from oxidation reactions to steam reforming and water-gas shift. Profile data up to the point of complete O2 consumption were used to develop a kinetic model for the oxidation chemistry. Structural data beyond the point of complete O2 consumption were ideal for demonstrating the correlative approach but the kinetic data in the second part were not considered during modeling because industrial selective oxidation reactors are always operated at incomplete O2 consumption. The fit of kinetic models to complete reactor profiles significantly speeds up the development and accuracy of kinetic models required for any reactor design. Further, the kinetic model considers the oxidation state of molybdenum as a dynamically changing and critical catalyst property. Hence, we could predict local catalyst oxidation states and validate our model experimentally with spatially-resolved XAS. This provides a quantitative link between catalyst structure and reactivity and allows including catalyst dynamics in reactor simulations. In the current work a widely applicable methodological approach is presented to understand and optimize heterogeneous catalytic processes, e.g. in selective oxidation.

Guidelines for the Molybdenum Oxidation State and Geometry from X-ray Absorption Spectroscopy at the Mo L2,3-Edges

Guidelines for the Molybdenum Oxidation State and Geometry from X-ray Absorption Spectroscopy at the Mo L_2,3-Edges

The reactions of MoOCl4 with neutral group 15 and 16 ligands and a re-investigation of some N-donor ligand complexes of MoOCl3

The reaction of molybdenum(VI) oxide tetrachloride, MoOCl4, with neutral ligands including MeCN, Ph3PO, SMe2, MeS(CH2)3SMe, SeMe2, PMe3, 2,2′-bipyridyl and 1,10-phenanthroline, results in reduction to form oxomolybdenum(V) complexes, identified by microanalysis, IR and UV/visible spectroscopy and via X-ray crystal structure analyses of several examples. Unexpectedly, the product formed with SeMe2 was [SeMe3]2[Mo2O2Cl6(μ-Cl)2] and with SMe2, [SMe2Cl]2[Mo2O2Cl6(μ-Cl)2]. X-ray crystal structures are reported for mer-[MoOCl3(MeCN)2], [{MoOCl2(MeCN)}2(µ-Cl)2], [MoOCl3{MeS(CH2)3SMe}], [SeMe3][MoOCl4(H2O)], [SMe2Cl]2[Mo2O2Cl6(μ-Cl)2] and [PMe3H][MoOCl4(PMe3)]. The reaction of MoOCl4 with [Et4N]Cl forms the dinuclear Mo(V) species, [Et4N]2[Mo2O2Cl6(μ-Cl)2].The red mer-[MoOCl3(diimine)] (diimine = 2,2′-bipyridyl, 1,10-phenathroline) complexes were prepared from [MoOCl3(thf)2] and the diimine and fully characterised by spectroscopy and by X-ray crystallography. The long-known ‘green isomers’ of [MoOCl3(diimine)] obtained from MoOCl4 and the diimines (and in other ways), are suggested to be the red isomers co-crystallised with another lower oxidation state molybdenum complex.

Chemical, mineralogical, and environmental characterization of tunnel boring muds for their valorization in road construction: a focus on molybdenum characterization.

Tunnel boring muds, coming from underground works, are considered as specific materials due to their intrinsic characteristics (granularity, clay content, water content, presence of heavy metals). In order to determine if they can be valorized in road construction or civil engineering, a complete characterization, including their environmental behavior, is necessary. Thus, the aim of this study is to characterize a tunnel boring mud sample from chemical, mineralogical, and environmental point of view. The studied material, a limestone mud, was characterized using different analytical techniques. Some pollutants and heavy metals were identified, such as sulfates and molybdenum (Mo), and specific analyses were performed to identify molybdenum speciation. As molybdenum was detected as traces in the studied material, it was necessary to increase its concentration. Thus, a nitric acid extraction was specifically developed at a laboratory scale with the aim to remove its high-calcium carbonate content. Then, synchrotron analyses were performed, allowing to obtain data on the oxidation state of molybdenum.

Enhanced photothermal conversion in nanometric scale MoOx multilayers with Al2O3 passivation layer

An optically selective stack based on molybdenum oxide nanometric layers (Mo/MoOx/Mo/MoO3/Al2O3) was designed using SCOUT reflectance simulations and fabricated using balanced magnetron sputtering for applications in solar thermal systems. The material properties were experimentally optimised by varying the process parameters namely: target power, gas flow rates, and deposition time. In the stack, the bottommost Mo metal layer is used to improve adhesion, reduce diffusion while acting as an infrared reflector, the MoOx layer of the tandem stack acts as the primary light absorbing layer, and the topmost MoO3 + Al2O3 layers act as anti-reflection layers. The individual layers of the optical stack exhibited an amorphous structure as confirmed using X-ray diffraction. The existence of lower oxidation states (+4, +5) of molybdenum in the MoOx layer was revealed by X-ray photoelectron spectroscopy. The stack achieved a high absorptance in the solar spectrum region (α = 0.969) and a low thermal emissivity in the infrared region (ε = 0.15 at 82 °C) at optimal process parameters. The oxidation resistance and thermal stability were evaluated by annealing the samples in vacuum up to 500 °C.

Mesoporous Molybdenum-Tungsten Mixed Metal Oxide: A Solid Acid Catalyst for Green, Highly Efficient sp3-sp2 C-C Coupling Reactions.

A mesoporous molybdenum tungsten mixed metal oxide with high surface area (173 m2/g) was synthesized by using metal dissolution coupled with a surfactant assisted reverse micelle formation synthesis method. Comprehensive characterization of the mixed oxide was performed by using PXRD, Raman, BET, SEM, EDX, TEM, and XPS. Thus, the formation of α-Mo0.5W0.5O3 with a homogeneous distribution of Mo and W throughout the material was seen. Furthermore, multiple oxidation states of molybdenum (Mo6+ and Mo5+) and a single oxidation state of tungsten (W6+) were observed. The weak/moderate acidic sites present in the mixed metal oxide resulted in excellent catalytic properties toward the sp3-sp2 carbon-carbon coupling reactions. The coupling of benzyl alcohol and toluene was completed within 15 min at 110 °C with 99% yield.

Catalytic hydrodeoxygenation of rubber seed oil over sonochemically synthesized Ni-Mo/γ-Al2O3 catalyst for green diesel production

Hydrodeoxygenation is one of the promising technologies for the transformation of triglycerides into long-chain hydrocarbon fuel commonly known as green diesel. The hydrodeoxygenation (HDO) of rubber seed oil into diesel range (C15–C18) hydrocarbon over non-sulphided bimetallic (Ni-Mo/γ-Al2O3 solid catalysts were studied. The catalysts were synthesized via wet impregnation method as well as sonochemical method. The synthesized catalysts were subjected to characterization methods including FESEM coupled with EDX, XRD, BET, TEM, XPS, NH3-TPD, CO-chemisorption and H2-TPR in order to investigate the effects of ultrasound irradiations on physicochemical properties of the catalyst. All the catalysts were tested for HDO reaction at 350 °C, 35 bar, H2/oil 1000 N (cm3/cm3) and WHSV = 1 h−1 in fixed bed tubular reactor. The catalyst prepared via sonochemical method showed comparatively higher specific surface area, particles in nano-size and uniform distribution of particle on the external surface of the support, higher crystallinity and lower reduction temperature as well as higher concentration of Mo4+ deoxygenating metal species. These physicochemical properties improved the catalytic activity compared to conventionally synthesized catalyst for HDO of rubber seed oil. The catalytic performance of sonochemically synthesized Ni-Mo/γ-Al2O3 catalyst (80.87%) was higher than the catalyst prepared via wet impregnation method (63.3%). The sonochemically synthesized Ni-Mo/γ-Al2O3 catalyst is found to be active, produces 80.87 wt% of diesel range hydrocarbons, and it gives high selectivity for Pentadecane (18.7 wt%), Hexadecane (16.65 wt%), Heptadecane (24.45 wt%) and Octadecane (21.0 wt%). The product distribution revealed that the deoxygenation reaction pathway was preferred. Higher conversion and higher HDO yield in this study are associated mainly with the change in concentration ratio between oxidation states of molybdenum (Mo4+, Mo5+, and Mo6+) on the external surface of the catalyst due to ultrasound irradiation during the synthesis process. Consequently, the application of sonochemically synthesized non-sulphided catalysts favored mainly hydrodeoxygenation of diesel range hydrocarbon.

Application of sandwich-type polyoxometalates modified TiO<sub>2</sub> in dye-sensitized solar cells

<p indent=0mm>Nowadays, the rapid consumption of fossil energy has led to global energy shortage. At present, more than 80% of the energy consumed globally is derived from non-renewable fossil fuels such as coal, oil and natural gas. The burning of fossil fuels will also bring about a series of problems such as the greenhouse effect, the falling quality of global air, the formation of acid rain and the pollution of water bodies. Therefore, whether new energy sources that can replace fossil energy can be found has become an increasingly popular concern problem. Dye-sensitized solar cells (DSSCs) as a new type of renewable energy source have attracted wide attention in recent years, because of their simple fabrication process, low production costs, relatively high photoelectric conversion efficiency (PCE), and being environmentally safe. But the recombinations of photogenerated electrons holes are seriously affected the photoelectric conversion efficiency of DSSCs. Polyoxometalates (POMs) are a class of metal oxide clusters with the highest oxidation state of tungsten, molybdenum or vanadium. Due to their structural diversity and unique physicochemical properties, they have been applied in catalysis, photochemistry, biology and medicine. However, due to POMs have excellent photoelectrochemical properties, which can be used as an excellent electronic extractant in the photoanode of DSSCs. Here, the sandwich-type polyoxometalates compound K₁₅{K₃[(A-α-PW₉O₃₄)₂Fe₂(C₂O₄)₂]}·29H₂O with the intramolecular electron transfer properties is composited with TiO₂ by sol-gel method to prepare a POM@TiO₂ composite photoanode. The energy band structure of the polyoxometalate is studied by optical and electrochemical measurements. The result shows that the LUMO energy level <sc>(-0.06 V)</sc> of the sandwich-type polyoxometalates is lower than that of TiO₂ and the optical band gap is <sc>2.28 eV.</sc> The performance test shows that the DSSC efficiency of POM@TiO₂ composite photoanode production reached 6.33%, which is 15% higher than that of battery whose anode is pure TiO₂ (5.52%). Electrochemical impedance spectroscopy (EIS), dark current tests and voltage decay curve tests demonstrate that sandwich-type POMs effectively suppress electron-hole recombinations and increase electron lifetime. The incident monochromatic photon-electron conversion efficiency (IPCE) test further demonstrates that the introduction of the POMs increases the monochromatic conversion efficiency (from 35% to 53%).

Electronic Structure and Nature of the Chemical Bonds of a Transition Metal with a Non-Innocent Ligand in Coordination Complex Na3[Mo(NO)(NH2O){N(CH2PO3)3H}] · 8H2O

A heteroleptic complex of molybdenum with nitrilotris(methylenephosphonic acid), hydroxylamine, and nitrogen(II) oxide is investigated via single-crystal X-ray diffraction (SXRD) and X-ray photoelectron spectroscopy (XPS). It is established that the actual charge on the Mo atom is around +1e, despite the formal oxidation state of molybdenum being +3. The electron density is mostly localized in the Mo–NO bond, and the distribution of the electron density is indicative of the formation of a π-bond.