Direct conversion of multilayer molybdenum trioxide to nanorods as multifunctional electrodes in lithium-ion batteries

Improved flame retardancy and smoke suppression properties of phenolic resin by incorporating MoO3 particles

Phenolic resin (PF) is widely used in aerospace, composite materials, and other fields. However, large amount of heat and smoke are produced during its combustion process, which is an important factor limiting its usage. To solve this problem, additive flame retardant MoO3 has been incorporated into PF for improving its flame retardancy and smoke suppression properties. Thermogravimetric analyses results show that the T5% of PF composites was gradually decreased from 264°C to 184°C and the char yield of PF-10% MoO3 is 57 wt.%, higher than that of neat PF (50 wt.%). The PF composites with 10 wt.% MoO3 passed UL-94 V-0 rating with a limiting oxygen index value of 29.8%. Meanwhile, the total heat release and total smoke production of PF-10% MoO3 are 37.60 MJ/m2 and 5.79 m2 respectively, which are reduced by 30.5% and 24.8% compared with neat PF. Only 10 wt.% MoO3 provide a 56.5% reduction (from 255 to 111) in maximal smoke density, meaning the good smoke suppression properties of MoO3. The pyrolysis products components are determined by thermogravimetric analysis combined with Fourier transform infrared spectroscopy. Furthermore, the micromorphology and chemical structure of char residue are also investigated by scanning electron microscopy, x-ray diffraction and Raman spectroscopy techniques. The promoting carbonization effect of MoO3 significantly reduces the heat release and toxic smoke production of PF composites.

Cathode materials with mixed phases of orthorhombic MoO3 and Li0.042MoO3 for lithium-ion batteries

MoO3 is a promising cathode candidate for lithium-ion batteries and its electronic conductivity is usually improved by MoO3lithiation via reaction of MoO3 with LiCl solutions. However, this process might increase the manufacturing complexity and result in surface breakage of MoO3 cathodes. In this paper, by introducing lithium source into MoO3 synthesis, MoO3 can be lithiated through introduction of the Li0.042MoO3 phase into the MoO3 structure. XRD and ICP results indicate that the phase composition and lithium content can be regulated by changing the amount of lithium source in the reaction solutions. FESEM and specific surface area measurements show that the particle size becomes more uniform and the surface area is increased when the degree of MoO3 lithiation is higher. The lithiated MoO3 sample shows better cycling performance than that of pristine MoO3, which is mainly due to the enhanced conductivity and increased surface area of the lithiated MoO3.

Modified top-down approach for synthesis of molybdenum oxide quantum dots: sonication induced chemical etching of thin films

A simple and modified top-down approach to synthesize molybdenum oxide (MoO_x: x = 2, 3) quantum dots (QDs) is proposed in this study. This modified approach involves the conversion of a bulk powder material into thin films followed by a sonication induced chemical etching process for synthesising QDs. X-Ray Diffraction (XRD) is used for crystal structural characterization of MoO_x thin films. The crystal structure properties of the MoO_x QDs are analysed by High Resolution Transmission Electron Microscopy (HRTEM) images and corresponding Selected Area Electron Diffraction (SAED) patterns. The optical band gap is estimated by Tauc's plot from UV-Vis-NIR absorption spectra. The excitation dependent photoluminescence (PL) emission of MoO_x QDs as a function of acid concentration is investigated. The growth mechanism of QDs in different crystalline phases as a function of acid concentration is also exemplified in this work. The micro-Raman and Fourier Transform of Infrared (FTIR) spectra are recorded to analyse the vibrational spectrum of the molybdenum–oxygen (Mo–O) bonds in the MoO_x QDs.

A simple and modified top-down approach to synthesize molybdenum oxide (MoO_x: x = 2, 3) quantum dots (QDs) is proposed in this study.

Oxygen vacancy-rich MoO3−x nanobelts for photocatalytic N2 reduction to NH3 in pure water

Photocatalytic nitrogen fixation is a promising sustainable and green strategy for NH₃ synthesis.

New Insights into Planar Defects in Layered α-MoO3 Crystals

The observation of regular ( h0 l) planar defects in α-MoO₃ crystals can be traced back to over 60 years ago. Two mechanisms have been proposed to interpret the formation of the planar defects. One is related to the diffusion of oxygen vacancies because of thermal-driven release of oxygen atoms in vacuum and the consequent crystallographic shear of α-MoO₃. The other is associated with redox reactions of moisture and/or hydrocarbons that give rise to H _xMoO₃ precipitates. Here, we report that regularly spaced (302) planar defects can be introduced into α-MoO₃ belt crystals by heating in liquid sulfur at 300 °C. These defects are undetectable by both atomic force microscopy and scanning electron microscopy at the crystal surface. Raman scattering enhancement and weakening have been observed for different phonon modes of α-MoO₃ at the (302) planar defects as probed from the (010) surface. Their comparisons with the Raman scattering enhancements at the edges and the argon-plasma-induced Raman spectral evolutions of the as-grown α-MoO₃ belt crystals provide new insights into the planar defects with regard to their formation and characteristics.

Molybdenum oxide quantum dots prepared via a one-step stirring strategy and their application as fluorescent probes for pyrophosphate sensing and efficient antibacterial materials

MoO_x QDs were prepared using a one-step stirring treatment of MoO₃ powder in DMSO. They can be used as efficient fluorescent probes and antibacterial materials.

Coupling interconnected MoO3/WO3 nanosheets with a graphene framework as a highly efficient anode for lithium-ion batteries

A rationally assembled three-dimensional graphene framework coupled with interconnected molybdenum/tungsten oxide nanosheets (MoO₃/WO₃-GF) has been developed via a one-step template-free strategy. With the unique nanostructure, the obtained anode material not only exhibits a high reversible capacity of about 1000 mA h g^-1, approaching the theoretical capacity of MoO₃ and WO₃ materials, but also shows excellent rate capability and cycling performance with negligible capacity attenuation after a long-time test. These features make it a promising candidate material for high-performance commercial lithium-ion batteries in the future.

Au-Loaded Hierarchical MoO3 Hollow Spheres with Enhanced Gas-Sensing Performance for the Detection of BTX (Benzene, Toluene, And Xylene) And the Sensing Mechanism

Monodisperse, hierarchical α-MoO₃ hollow spheres were fabricated using a facile template-free solvothermal method combined with subsequent calcination. Various quantities of Au nanoparticles (NPs) were deposited on the α-MoO₃ hollow spheres to construct hybrid nanomaterials for chemical gas sensors and their BTX sensing properties were investigated. The 2.04 wt % Au-loaded α-MoO₃ sensor can detect BTX effectively at 250 °C, especially, its responses to 100 ppm toluene and xylene are 17.5 and 22.1, respectively, which are 4.6 and 3.9 times higher than those of pure α-MoO₃ hollow spheres at 290 °C. Besides, Au loading decreased the response times to toluene and xylene from 19 and 6 s to 1.6 and 2 s, respectively, lowered the working temperature from 290 to 250 °C as compared with those of pure α-MoO₃. The surface status of Au/α-MoO₃ hollow spheres before and after contacting with toluene at 250 °C was analyzed through XPS technique. Possible oxidization product of toluene was confirmed by GC for the first time. The gas-sensing mechanism of the Au/α-MoO₃ was speculated as the oxidation of toluene to water and carbon dioxide by chemisorbed oxygen and lattice oxygen. The possible reason related with improved gas-sensing properties of the Au-functionalized α-MoO₃ was discussed.

Highly Photoluminescent Molybdenum Oxide Quantum Dots: One-Pot Synthesis and Application in 2,4,6-Trinitrotoluene Determination

As a well-studied transition-metal semiconductor material, MoOx has a wider band gap than molybdenum disulfide (MoS2), and its property varies dramatically for the existence of several different allotropes and suboxide phases of molybdenum oxides (MoOx, x < 3). In this manuscript, a one-pot method possessing the advantages of one pot, easily prepared, rapid, and environmentally friendly, has been developed for facile synthesis of highly photoluminescent MoOx quantum dots (MoOx QDs), in which commercial molybdenum disulfide (MoS2) powder and hydrogen peroxide (H2O2) are employed as the precursor and oxidant, respectively. The obtained MoOx QDs can be further utilized as an efficient photoluminescent probe, and a new turn-off sensor is developed for 2,4,6-trinitrotoluene (TNT) determination based on the fact that the photoluminescence of MoOx QDs can be quenched by the Meisenheimer complexes formed in the strong alkali solution through the inner filter effect (IFE). Under the optimal conditions, the decreased photoluminescence of MoOx QDs shows a good linear relationship to the concentration of TNT ranging from 0.5 to 240.0 μM, and the limit of detection was 0.12 μM (3σ/k). With the present turn-off sensor, TNT in river water samples can be rapidly and selectively detected without tedious sample pretreatment processes.

Iso-oriented monolayer α-MoO3(010) films epitaxially grown on SrTiO3(001)

The ability to synthesize well-ordered two-dimensional materials under ultra-high vacuum and directly characterize them by other techniques in situ can greatly advance our current understanding on their physical and chemical properties. In this paper, we demonstrate that iso-oriented α-MoO3 films with as low as single monolayer thickness can be reproducibly grown on SrTiO3(001) substrates by molecular beam epitaxy ((010)(MoO3)‖(001)(STO), [100](MoO3)‖[100](STO) or [010](STO)) through a self-limiting process. While one in-plane lattice parameter of the MoO3 is very close to that of the SrTiO3 (a(MoO3) = 3.96 Å, a(STO) = 3.905 Å), the lattice mismatch along other direction is large (∼5%, c(MoO3) = 3.70 Å), which leads to relaxation as clearly observed from the splitting of streaks in reflection high-energy electron diffraction (RHEED) patterns. A narrow range in the growth temperature is found to be optimal for the growth of monolayer α-MoO3 films. Increasing deposition time will not lead to further increase in thickness, which is explained by a balance between deposition and thermal desorption due to the weak van der Waals force between α-MoO3 layers. Lowering growth temperature after the initial iso-oriented α-MoO3 monolayer leads to thicker α-MoO3(010) films with excellent crystallinity.

Enhanced Reaction Kinetics and Structure Integrity of Ni/SnO2 Nanocluster toward High-Performance Lithium Storage

SnO2 is regarded as one of the most promising anodes via conversion-alloying mechanism for advanced lithium ion batteries. However, the sluggish conversion reaction severely degrades the reversible capacity, Coulombic efficiency and rate capability. In this paper, through constructing porous Ni/SnO2 composite electrode composed of homogeneously distributed SnO2 and Ni nanoparticles, the reaction kinetics of SnO2 is greatly enhanced, leading to full conversion reaction, superior cycling stability and improved rate capability. The uniformly distributed Ni nanoparticles provide a fast charge transport pathway for electrochemical reactions, and restrict the direct contact and aggregation of SnO2 nanoparticles during cycling. In the meantime, the void space among the nanoclusters increases the contact area between the electrolyte and active materials, and accommodates the huge volume change during cycling as well. The Ni/SnO2 composite electrode possesses a high reversible capacity of 820.5 mAh g(-1) at 1 A g(-1) up to 100 cycles. More impressively, large capacity of 841.9, 806.6, and 770.7 mAh g(-1) can still be maintained at high current densities of 2, 5, and 10 A g(-1) respectively. The results demonstrate that Ni/SnO2 is a high-performance anode for advanced lithium-ion batteries with high specific capacity, excellent rate capability, and cycling stability.

Reduced graphene oxide-wrapped MoO3 composites prepared by using metal-organic frameworks as precursor for all-solid-state flexible supercapacitors

Reduced graphene oxide-wrapped MoO3M (rGO/MoO3 ) is prepared by a novel and simple method that is developed by using a metal-organic framework as the precursor. After a two-step annealing process, the obtained rGO/MoO3 composite is used for a high-performance supercapacitor electrode. Moreover, an all-solid-state flexible supercapacitor is fabricated based on the rGO/MoO3 composite, which shows stable performance under different bending states.

An ultraselective and ultrasensitive TEA sensor based on α-MoO3 hierarchical nanostructures and the sensing mechanism

Flower-like α-MoO₃ hierarchical nanostructures were successfully synthesized via a single-step solvothermal route. A sensor based on α-MoO₃ flowers manifested superior gas sensing performance towards TEA at 170 °C.

Facile synthesis of nanostructured carbon nanotube/iron oxide hybrids for lithium-ion battery anodes

Nanostructured carbon nanotubes/iron oxide hybrids (CNIOHs) were synthesized by a scalable Bake-Break-Mix process which involves three simple steps.