V2 O3 Research Articles

Self-Zincophilic Dual Protection Host of 3D ZnO/Zn⊂CF to Enhance Zn Anode Cyclability.

Zn dendrite growth and side reactions restrict the practical use of Zn anode. Herein, the design of a novel 3D hierarchical structure is demonstrated with self-zincophilic dual-protection constructed by ZnO and Zn nanoparticles immobilized on carbon fibers (ZnO/Zn⊂CF) as a versatile host on the Zn surface. The unique 3D frameworks with abundant zinc nucleation storage sites can alleviate the structural stress during the plating/stripping process and overpower Zn dendrite growth by moderating Zn2+ flux. Moreover, given the dual protection design, it can reduce the contact area between active zinc and electrolyte, inhibiting hydrogen evolution reactions. Importantly, density functional theory calculations and experimental results confirm that the introduced O atoms in ZnO/Zn⊂CF enhance the interaction between Zn2+ and the host and reduce Zn nucleation overpotential. As expected, the ZnO/Zn⊂CF-Zn electrode exhibits stable Zn plating/stripping with low polarization for 4200h at 0.2mAcm-2 and 0.2 mAhcm-2. Furthermore, the symmetrical cell displays a significantly long cycling life of over 1800h, even at 30mAcm-2. The fabricated full cells also show impressive cycling performance when coupled with V2O3 cathodes.

Hyphae Carbon Coupled with Gel Composite Assembly for Construction of Advanced Carbon/Sulfur Cathodes for Lithium-Sulfur Batteries.

The design and fabrication of novel carbon hosts with high conductivity, accelerated electrochemical catalytic activities, and superior physical/chemical confinement on sulfur and its reaction intermediates polysulfides are essential for the construction of high-performance C/S cathodes for lithium-sulfur batteries (LSBs). In this work, a novel biofermentation coupled gel composite assembly technology is developed to prepare cross-linked carbon composite hosts consisting of conductive Rhizopus hyphae carbon fiber (RHCF) skeleton and lamellar sodium alginate carbon (SAC) uniformly implanted with polarized nanoparticles (V2O3, Ag, Co, etc.) with diameters of several nanometers. Impressively, the RHCF/SAC/V2O3 composites exhibit enhanced physical/chemical adsorption of polysulfides due to the synergistic effect between hierarchical pore structures, heteroatoms (N, P) doping, and polar V2O3 generation. Additionally, the catalytic conversion kinetics of cathodes are effectively improved by regulating the 3D carbon structure and optimizing the V2O3 catalyst. Consequently, the LSBs assembled with RHCF/SAC/V2O3-S cathode show exceptional cycle stability (capacity retention rate of 94.0% after 200 cycles at 0.1 C) and excellent rate performance (specific capacity of 578mA h g-1 at 5 C). This work opens a new door for the fabrication of hyphae carbon composites via fermentation for electrochemical energy storage.

Crystal structure of (μ-hydrogen di-sulfato)-μ-oxido-bis-[(4,4'-di-tert-butyl-2,2'-bi-pyridine)-oxidovanadium(IV/V)] aceto-nitrile monosolvate.

The dinuclear oxidovanadium(IV/V) complex, [V2(HS2O8)O3(C18H24N2)2]·CH3CN or [V2O2(μ-O)(μ-H(SO4)2)(4,4'-tBubpy)2]·CH3CN (4,4'-tBubpy = 4,4'-di-tert-butyl-2,2'-bi-pyridine), has crystallographic C 2 symmetry and exhibits a distorted octa-hedral geometry around the vanadium center, where the two 4,4'-tBubpy ligands are nearly orthogonal to each other. The two vanadium ions are linked by an oxo anion and a unique protonated sulfate anion [H(SO4)2 3-]. In the crystal, inter-molecular C-H⋯π and π-π inter-actions between the 4,4'-tBubpy ligands are present, leading to a three-dimensional network.

Voltage-Modulated Untwist Deformations and Multispectral Optical Effects from Ion Intercalation into Chiral Ceramic Nanoparticles.

Reconfiguration of chiral ceramic nanostructures after ion intercalation should favor specific nanoscale twists leading to strong chiroptical effects. In this work, V2 O3 nanoparticles are shown to have "built-in" chiral distortions caused by binding of tartaric acid enantiomers to the nanoparticle surface. As evidenced by spectroscopy/microscopy techniques and calculations of nanoscale chirality measures, the intercalation of Zn2+ ions into the V2 O3 lattice results in particle expansion, untwist deformations, and chirality reduction. Coherent deformations in the particle ensemble manifest as changes in sign and positions of circular polarization bands at ultraviolet, visible, mid-infrared (IR), near-IR (NIR), and IR wavelengths. The g-factors observed for IR and NIR spectral diapasons are ≈100-400 times higher than those for previously reported dielectric, semiconductor, and plasmonic nanoparticles. Nanocomposite films layer-by-layer assembled (LBL) from V2 O3 nanoparticles reveal cyclic-voltage-driven modulation of optical activity. Device prototypes for IR and NIR range problematic for liquid crystals and other organic materials are demonstrated. High optical activity, synthetic simplicity, sustainable processability, and environmental robustness of the chiral LBL nanocomposites provide a versatile platform for photonic devices. Similar reconfigurations of particle shapes are expected for multiple chiral ceramic nanostructures, leading to unique optical, electrical, and magnetic properties.

In Situ X-ray Diffraction Studies on the Reduction of V2 O5 and WO3 by Using Hydrogen.

The reduction of metal oxides with hydrogen is widely used for the production of fine chemicals and metals both on the laboratory and industry scale. In situ methods can help to elucidate reaction pathways and to gain control over such synthesis reactions. In this study, the reduction of WO3 and V2 O5 with hydrogen was investigated by in situ X-ray powder diffraction with regard to intermediates and the influence of heating rates and hydrogen flow rates. Mixtures of V4 O9 , V6 O13 and VO2 in two modifications were identified as intermediates on the way to phase-pure V2 O3 . None of the intermediates occurs in a single phase and therefore cannot be prepared this way. In contrast, the intermediates of the WO3 reduction, H0.23 WO3 and W10 O29 , appear consecutively and can be isolated. For both reactions, the heating and flow rates have little influence on the formation of intermediates.

Interfacial Engineering of Ni/V2 O3 Heterostructure Catalyst for Boosting Hydrogen Oxidation Reaction in Alkaline Electrolytes.

Alkaline fuel cells can permit the adoption of platinum group metal-free (PGM-free) catalysts and cheap bipolar plates, thus further lowering the cost. With the exploration of PGM-free hydrogen oxidation reaction (HOR) catalysts, nickel-based compounds have been considered as the most promising HOR catalysts in alkali. Here we report an interfacial engineering through the formation of nickel-vanadium oxide (Ni/V2 O3 ) heterostructures to activate Ni for efficient HOR catalysis in alkali. The strong electron transfer from Ni to V2 O3 could modulate the electronic structure of Ni sites. The optimal Ni/V2 O3 catalyst exhibits a high intrinsic activity of 0.038 mA cm-2 and outstanding stability. Experimental and theoretical studies reveal that Ni/V2 O3 interface as the active sites can enable to optimize the hydrogen and hydroxyl bindings, as well as protect metallic Ni from extensive oxidation, thus achieving the notable activity and durability.

Interface Metal Oxides Regulating Electronic State around Nickel Species for Efficient Alkaline Hydrogen Electrocatalysis.

Heterogeneous electrocatalysis typically depends on the surface electronic states of active sites. Modulating the surface charge state of an electrocatalysts can be employed to improve performance. Among all the investigated materials, nickel (Ni)-based catalysts are the only non-noble-metal-based alternatives for both hydrogen oxidation and evolution reactions (HOR and HER) in alkaline electrolyte, while their activities should be further improved because of the unfavorable hydrogen adsorption behavior. Hereto, Ni with exceptional HOR electrocatalytic performance by changing the d-band center by metal oxides interface coupling formed in situ is endowed. The resultant MoO2 coupled Ni heterostructures exhibit an apparent HOR activity, even approaching to that of commercial 20% Pt/C benchmark, but with better long-term stability in alkaline electrolyte. An exceptional HER performance is also achieved by the Ni-MoO2 heterostructures. The experiment results are rationalized by the theoretical calculations, which indicate that coupling MoO2 with Ni results in the downshift of d-band center of Ni, and thus weakens hydrogen adsorption and benefits for hydroxyl adsorption. This concept is further proved by other metal oxides (e.g., CeO2 , V2 O3 , WO3 , Cr2 O3 )-formed Ni-based heterostructures to engineer efficient hydrogen electrocatalysts.

Crystal Surface Engineering Induced Active Hexagonal Co2 P-V2 O3 for Highly Stable Lithium-Sulfur Batteries.

Purposeful control of the highly active crystal planes is an effective strategy to improve the nanocrystalline catalytic activity. Therefore, Co2 P nanocrystals with high exposure of (211) lattice plane loaded at 2D hexagonal V2 O3 nanosheets (H-Co2 P-V2 O3 ) are designed via the control of morphology. After optimization, this H-Co2 P-V2 O3 boosts the redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSBs), which is due to the increase of the Co-active sites by exposing more (211) lattice planes of Co2 P, and the high adsorption and catalysis characteristic of H-Co2 P-V2 O3 for the conversion of LiPSs into LSBs. In the case of modification separator by H-Co2 P-V2 O3 composite, the battery achieves an outstanding reversibility of 876.9 mAh g-1 over 500 cycles at 1 C, a superior rate property of 611.5 mAh g-1 at 8 C, and a long-term cycling performance with a low attenuation of 0.04% per cycle over 1000 cycles at 4 C for LSBs. Impressively, a remarkable areal capacity of 12.38 mAh cm-2 is retained under the high sulfur loading of 14.5mg cm-2 after 100 cycles. It is believed that the crystal surface engineering provides guidance to further improve the electrochemical performance of the LSB field.

Rapid Electrochemical Activation of V2O3@C Cathode for High‐Performance Zinc‐Ion Batteries in Water‐in‐Salt Electrolyte

Aqueous Zn-ion batteries (ZIBs), with the advantages of low cost, high safety, and high capacity, have great potential for application in grid energy storage and wearable flexible devices. However, their commercial application is still restricted by their inferior long-term cycling stability, Zn dendrite formation, and the decomposition of aqueous electrolyte. In this study, a Zn|Zn(CF3 SO3 )2 +LiTFSI|V2 O3 @C cell is constructed to address the above issues. The V2 O3 @C electrode can be fully oxidized into amorphous V2 O5 @C simultaneously with Zn2+ and H2 O co-insertion. The cell delivers a high specific capacity of more than 240 mAh g-1 at 3 A g-1 , with extraordinary coulombic efficiency and capacity retention. The excellent electrochemical performances are attributed to synergistic effects between the V2 O3 @C electrode and the water-in-salt electrolyte with enhanced stability and improved interface reaction kinetics. Systematic improvements of this architecture indicate much promise for application.

V2 O3 /MnS Arrays as Bifunctional Air Electrode for Long-Lasting and Flexible Rechargeable Zn-Air Batteries.

Exploring highly efficient, stable, and cost-effective bifunctional electrocatalysts is crucial for the wide commercialization of rechargeable Zn-air batteries. Herein, a vanadium-oxide-based hybrid air electrode comprising a heterostructure of V2 O3 and MnS (V2 O3 /MnS) is reported. The V2 O3 /MnS catalyst shows a decent catalytic activity that is comparable to Pt/C toward the oxygen reduction reaction and acceptable toward oxygen evolution. The extraordinary stability as well as the low cost set the V2 O3 /MnS among the best bifunctional oxygen electrocatalysts. In a demonstration of an assembled liquid-state Zn-air battery using V2 O3 /MnS as cathode, high power density (118mW cm-2 ), specific capacity (808 mAh gZn -1 ), and energy density (970Wh kgZn -1 ), as well as the outstanding rechargeability and durability for 4000 cycles (>1333 h, i.e., >55days) are enabled. The V2 O3 /MnS is also integrated into an all-solid-state Zn-air battery to demonstrate its great potential as a flexible power source for next-generation electronics. Density functional theory calculations further elucidate the origin of the intrinsic activity and stability of the V2 O3 /MnS heterostructure.

Vanadium oxides modify the expression levels of the p21, p53, and Cdc25C proteins in human lymphocytes treated in vitro.

In vitro assays have demonstrated that vanadium compounds interact with biological molecules similar to protein kinases and phosphatases and have also shown that vanadium oxides decrease the proliferation of cells, including human lymphocytes; however, the mechanism, the phase in which the cell cycle is delayed and the proteins involved in this process are unknown. Therefore, we evaluated the effects of vanadium oxides (V2 O3 , V2 O4 and V2 O5 ) in human lymphocyte cultures (concentrations of 2, 4, 8, or 16 μg/ml) on cellular proliferation and the levels of the p53, p21 and Cdc25C proteins. After 24 h of treatment with the different concentrations of vanadium oxides, the cell cycle phases were determined by evaluating the DNA content using flow cytometry, and the levels of the p21, p53 and Cdc25C proteins were assessed by Western blot analysis. The results revealed that the DNA content remained unchanged in every phase of the cell cycle; however, only at high concentrations did protein levels increase. Although, according to previous reports, vanadium oxides induce a delay in proliferation, DNA analysis did not show this occurring in a specific cell cycle phase. Nevertheless, the increases in p53 protein levels may cause this delay.

Surface Action Spectroscopy: A Review and a Perspective on a New Technique to Study Vibrations at Surfaces.

A new vibrational spectroscopy method aimed at the investigation of solid surfaces in ultrahigh vacuum, called "Surface Action Spectroscopy (SAS)", is described and the first results are reviewed. This technique is based on ideas and experiments performed in the gas phase. A surface is exposed to a messenger species at low temperature. This messenger species is desorbed via absorption of tunable infrared light from a free-electron laser and the desorption rate of the messenger species is recorded via mass spectrometry. It is shown that the technique is extremely surface sensitive and we discuss the basic mechanisms of the technique. We show a feasibility study on a V2 O3 (0001) surface, where we know the surface structure. We then proceed to the example of iron oxide films to study the surface structure in parallel with calculations of the surface phonons, which allow us to confirm the surface structure of Fe3 O4 (111) to be Fetet terminated. It also provides evidence for the so-called biphase structure. To conclude, we discuss possibilities to apply the technique to interesting questions in model and real catalysis, since the technique may provide interesting information independent of long-range order of the sample.

Free-Standing, Foldable V2 O3 /Multichannel Carbon Nanofibers Electrode for Flexible Li-Ion Batteries with Ultralong Lifespan.

Free-standing electrodes with high energy density and long life are of critical importance to the development of lithium-ion batteries (LIBs) for flexible/wearable electronic devices. Herein, the free-standing and foldable V2 O3 /multichannel carbon nanofibers (V2 O3 /MCCNFs) composites are prepared via electrospinning and subsequent carbonization. Such V2 O3 /MCCNFs electrode delivers a superior capacity of 881.1 mAh g-1 at 0.1 A g-1 after 240 cycles. More importantly, the ultralong lifespan is achieved with a high capacity of 487.8 mAh g-1 even after 5000 cycles at a high current density of 5 A g-1 with only 0.00323% decay rate, which shows the best performance among the reported V2 O3 -based anodes and other metal oxides based free-standing anodes. Furthermore, this flexible electrode is further applied to the pouch cell, which exhibits prominent capacity of 348.3 mAh g-1 after 500 cycles at 1 A g-1 with 0.094% decay per cycle. The unprecedented performance can be ascribed to synergetic contributions of V2 O3 and multichannel carbon nanofibers, which not only promote the penetration of electrolyte and reduce the transport length of Li+ , but also increase active material/electrolyte contact area and buffer the volume change. This work paves the way to develop free-standing electrode for flexible/wearable electronic devices with ultralong lifespan.

Al2 O3 -Assisted Confinement Synthesis of Oxide/Carbon Hollow Composite Nanofibers and Application in Metal-Ion Capacitors.

Hollow micro-/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a "top-down" casting process based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic-layer-deposition (ALD) Al2 O3 layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)-carbon composite hollow fibers after removal of Al2 O3 . Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni-based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for energy applications. Herein, the as-obtained hollow V2 O3 -C fiber membrane is employed as a freestanding and flexible electrode for lithium-ion capacitor. The device shows an impressive energy density and a high power density.

Boosting Alkaline Hydrogen Evolution Electrocatalysis over Metallic Nickel Sites through Synergistic Coupling with Vanadium Sesquioxide.

For renewable and sustainable energy, developing cut-price and high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) by alkaline water electrolysis is of paramount importance. In this study, a compound electrocatalyst composed of nickel-vanadium sesquioxide nanoparticles supported on porous nickel foam (Ni-V2 O3 /NF) is found to exhibit electrocatalytic performance towards HER that is superior to that of the commercial Pt/C catalyst, with nearly zero onset overpotential, an extremely low overpotential of 25 mV to obtain a current density of -10 mA cm-2 , a Tafel slope of 58 mV dec-1 , and a good durability for 24 h in 1.0 m KOH. Theoretical calculations reveal that the presence of V2 O3 optimizes the electronic structure of active Ni components and continuously accelerates the dissociation of water molecules, which in turn improves the HER kinetics. The present work will advance the development of highly efficient nanocomposite electrocatalysts for alkaline water electrocatalysis.

Metal-Organic Framework Derived Hierarchical Co/C@V2 O3 Hollow Spheres as a Thin, Lightweight, and High-Efficiency Electromagnetic Wave Absorber.

Developing high-efficiency electromagnetic (EM) wave absorbing materials with light weight, thin thickness, and wide absorption bandwidth is highly desirable for ever-developing electronic and telecommunication devices. Herein, hierarchical metal-organic framework (MOF)-derived Co/C@V2 O3 hollow spheres were designed and synthesized through a facile hydrothermal, precipitation, and pyrolysis method. The composite exhibits both excellent impedance matching and light weight due to the rational combination of hollow V2 O3 spheres and porous Co/C. Additionally, multiple components enable a large dielectric and magnetic loss of the composite, giving rise to enhanced EM wave absorption performance with a maximum reflection loss (RL) of -40.1 dB and a broad effective absorption bandwidth (RL < -10 dB) of 4.64 GHz at a small thickness of 1.5 mm. This work provides insights into the design of hierarchical hollow and porous composites as thin and lightweight EM wave absorbers with efficient absorption, which can also be extended to energy storage, catalysis, and sensing.

Multidimensional Synergistic Nanoarchitecture Exhibiting Highly Stable and Ultrafast Sodium‐Ion Storage

Conversion-type anodes with multielectron reactions are beneficial for achieving a high capacity in sodium-ion batteries. Enhancing the electron/ion conductivity and structural stability are two key challenges in the development of high-performance sodium storage. Herein, a novel multidimensionally assembled nanoarchitecture is presented, which consists of V2 O3 nanoparticles embedded in amorphous carbon nanotubes that are then coassembled within a reduced graphene oxide (rGO) network, this materials is denoted V2 O3 ⊂C-NTs⊂rGO. The selective insertion and multiphase conversion mechanism of V2 O3 in sodium-ion storage is systematically demonstrated for the first time. Importantly, the naturally integrated advantages of each subunit synergistically provide a robust structure and rapid electron/ion transport, as confirmed by in situ and ex situ transmission electron microscopy experiments and kinetic analysis. Benefiting from the synergistic effects, the V2 O3 ⊂C-NTs⊂rGO anode delivers an ultralong cycle life (72.3% at 5 A g-1 after 15 000 cycles) and an ultrahigh rate capability (165 mAh g-1 at 20 A g-1 , ≈30 s per charge/discharge). The synergistic design of the multidimensionally assembled nanoarchitecture produces superior advantages in energy storage.

Hierarchical Porous Intercalation-Type V2 O3 as High-Performance Anode Materials for Li-Ion Batteries.

As intercalation-type anode materials for Li-ion batteries (LIBs), the commercially used graphite and Li4 Ti5 O12 exhibit good cycling and rate properties, but their theoretical specific capacities are too low to meet the ever-growing demands of high-energy applications such as electric vehicles. Therefore, the development of new intercalation-type anode materials with larger capacity is very desirable. Herein, we design and synthesize novel 3 D hierarchical porous V2 O3 @C micro/nanostructures consisting of crumpled nanosheets, through self-reduction under annealing from the structurally similar VO2 (B)@C precursors without the addition of any other reducing reagent or gas. Excitingly, it is found for the first time through ex situ XRD technology that V2 O3 is a new, promising intercalation-type anode material for LIBs with a high capacity. V2 O3 @C micro/nanostructures can deliver a large capacity of 732 mAh g-1 without capacity loss at 100 mA g-1 even after 136 cycles, as well as exhibiting excellent cycling and rate performances. The application of V2 O3 for Na-ion batteries (NIBs) is elaborated for the first time, and excitingly, it is found that V2 O3 @C micro/nanostructures may be promising anode materials for NIBs.

Indirect determination of equilibrium distribution of V and Cr between liquid slag and solid iron at 1653 K and 101.3 kPa

In the present study, an indirect determination of equilibrium distributions of V and Cr between liquid FeO-SiO2 -MnO-TiO2 -V2 O3 -Cr2 O3 -MgO slag and solid iron was performed at 1653 K and 101.3 kPa. The experimental results were transformed to investigate the distributions of V and Cr between liquid vanadium-chromium slag and liquid iron. It was found that the distribution ratios determinated by indirect equilibrium method are slightly higher than that determinated by direct equilibrium method. Higher FeO content and lower SiO2 content have positive effect on the distribution ratios of V and Cr. However, Cr2 O3 and V2 O3 in slag have little influence on the distribution ratios of V and Cr, respectively. Furthermore, the distribution ratios of V and Cr decrease distinctly with increasing temperature.

Generic Synthesis of Carbon Nanotube Branches on Metal Oxide Arrays Exhibiting Stable High-Rate and Long-Cycle Sodium-Ion Storage.

A new and generic strategy to construct interwoven carbon nanotube (CNT) branches on various metal oxide nanostructure arrays (exemplified by V2 O3 nanoflakes, Co3 O4 nanowires, Co3 O4 -CoTiO3 composite nanotubes, and ZnO microrods), in order to enhance their electrochemical performance, is demonstrated for the first time. In the second part, the V2 O3 /CNTs core/branch composite arrays as the host for Na(+) storage are investigated in detail. This V2 O3 /CNTs hybrid electrode achieves a reversible charge storage capacity of 612 mAh g(-1) at 0.1 A g(-1) and outstanding high-rate cycling stability (a capacity retention of 100% after 6000 cycles at 2 A g(-1) , and 70% after 10 000 cycles at 10 A g(-1) ). Kinetics analysis reveals that the Na(+) storage is a pseudocapacitive dominating process and the CNTs improve the levels of pseudocapacitive energy by providing a conductive network.