/Tag: VS2

Novel single-layer vanadium sulphide phases. (arXiv:1803.07999v1 [cond-mat.mtrl-sci])

2018-03-22T19:59:15+00:00March 22nd, 2018|Categories: Publications|Tags: , |

VS2 is a challenging material to prepare stoichiometrically in the bulk, and the single layer has not been successfully isolated before now. Here we report the first realization of single-layer VS2, which we have prepared epitaxially with high quality on Au(111) in the octahedral (1T) structure. We find that we can deplete the VS2 lattice of S by annealing in vacuum so as to create an entirely new two-dimensional compound that has no bulk analogue. The transition is reversible upon annealing in an H2S gas atmosphere. We report the structural properties of both the stoichiometric and S-depleted compounds on the basis of low-energy electron diffraction, X-ray photoelectron spectroscopy and diffraction, and scanning tunneling microscopy experiments.

Published in: "arXiv Material Science".

Fast Li+ Diffusion in Interlayer-Expanded Vanadium Disulfide Nanosheets for Li+/Mg2+ Hybrid-Ion Batteries

2018-03-08T21:18:05+00:00March 8th, 2018|Categories: Publications|Tags: |

J. Mater. Chem. A, 2018, Accepted ManuscriptDOI: 10.1039/C8TA00418H, PaperYuan Meng, Yingying Zhao, Dashuai Wang, Di Yang, Yu Gao, Ruqian Lian, Gang Chen, Yingjin WeiLi+/Mg2+ hybrid-ion batteries (LMIBs) have attracted intensive attention because they can circumvent some serious drawbacks of Li- and Mg-rechargeable batteries.

Published in: "Journal of Materials Chemistry A".

Synergistic Interlayer and Defect Engineering in VS2 Nanosheets toward Efficient Electrocatalytic Hydrogen Evolution Reaction

2017-12-27T10:30:34+00:00December 27th, 2017|Categories: Publications|Tags: , |

Abstract A simple one-pot solvothermal method is reported to synthesize VS2 nanosheets featuring rich defects and an expanded (001) interlayer spacing as large as 1.00 nm, which is a ≈74% expansion as relative to that (0.575 nm) of the pristine counterpart. The interlayer-expanded VS2 nanosheets show extraordinary kinetic metrics for electrocatalytic hydrogen evolution reaction (HER), exhibiting a low overpotential of 43 mV at a geometric current density of 10 mA cm−2, a small Tafel slope of 36 mV dec−1, and long-term stability of 60 h without any current fading. The performance is much better than that of the pristine VS2 with a normal interlayer spacing, and even comparable to that of the commercial Pt/C electrocatalyst. The outstanding electrocatalytic activity is attributed to the expanded interlayer distance and the generated rich defects. Increased numbers of exposed active sites and modified electronic structures are achieved, resulting in an optimal free energy of hydrogen adsorption (∆GH) from density functional theory calculations. This work opens up a new door for developing transition-metal dichalcogenide nanosheets as high active HER electrocatalysts by interlayer and defect engineering. VS2 nanosheets featuring rich defects and an expanded (001) interlayer spacing as large as 1.00 nm are synthesized by a solvothermal method and demonstrate extraordinary kinetic metrics for the hydrogen evolution reaction. The electrocatalytic activity enhancement is attributed to the optimal free energy of hydrogen adsorption (∆GH) based on the molecular simulation.

Published in: "Small".

Elastic Sandwich-Type rGO–VS2/S Composites with High Tap Density: Structural and Chemical Cooperativity Enabling Lithium–Sulfur Batteries with High Energy Density

2017-12-27T10:28:58+00:00December 27th, 2017|Categories: Publications|Tags: , , , |

Abstract Driven by increasing demand for high-energy-density batteries for consumer electronics and electric vehicles, substantial progress is achieved in the development of long-life lithium–sulfur (Li–S) batteries. Less attention is given to Li–S batteries with high volume energy density, which is crucial for applications in compact space. Here, a series of elastic sandwich-structured cathode materials consisting of alternating VS2-attached reduced graphene oxide (rGO) sheets and active sulfur layers are reported. Due to the high polarity and conductivity of VS2, a small amount of VS2 can suppress the shuttle effect of polysulfides and improve the redox kinetics of sulfur species in the whole sulfur layer. Sandwich-structured rGO–VS2/S composites exhibit significantly improved electrochemical performance, with high discharge capacities, low polarization, and excellent cycling stability compared with their bare rGO/S counterparts. Impressively, the tap density of rGO–VS2/S with 89 wt% sulfur loading is 1.84 g cm−3, which is almost three times higher than that of rGO/S with the same sulfur content (0.63 g cm−3), and the volumetric specific capacity of the whole cell is as high as 1182.1 mA h cm−3, comparable with the state-of-the-art reported for energy storage devices, demonstrating the potential for application of these composites in long-life and high-energy-density Li–S batteries. The elastic sandwich-type composites of alternating reduced graphene oxide (rGO)–vanadium disulfide (VS2) sheets and pure sulfur layers are fabricated using conductive VS2 as a shape-directed agent. The rGO–VS2/S with an 89 wt% sulfur loading shows high tap density and striking volumetric specific capacity. The excellent electrochemical performance holds great potential

Published in: "Advanced Energy Materials".

Two-dimensional VS2 Monolayers as Potential Anode Materials for Lithium-ion Batteries and Beyond: First-Principles Calculations

2017-09-16T15:18:19+00:00September 16th, 2017|Categories: Publications|Tags: |

J. Mater. Chem. A, 2017, Accepted ManuscriptDOI: 10.1039/C7TA06944H, PaperDashuai Wang, Yanhui Liu, Xing Meng, Yingjin Wei, Yingying Zhao, Qiang Pang, Gang ChenFirst-principles calculations based on density functional theory were carried out to investigate the electrochemical performance of monolayer VS2 for Li-, K-, Mg-

Published in: "Journal of Materials Chemistry A".

Facile In-Situ Synthesis of Crystalline VOOH-Coated VS2 Microflowers with Superior Sodium Storage Performance

2017-08-30T23:18:10+00:00August 30th, 2017|Categories: Publications|Tags: |

J. Mater. Chem. A, 2017, Accepted ManuscriptDOI: 10.1039/C7TA05205G, PaperWenbin Li, Jianfeng Huang, Liangliang Feng, Liyun CAO, Yongqiang Feng, Haijing Wang, Jiayin Li, Chunyan YaoThe meticulous design of coating structure is an efficient approach for enhancing the cycling life and rate capability of electrode

Published in: "Journal of Materials Chemistry A".

Degradable Vanadium Disulfide Nanostructures with Unique Optical and Magnetic Functions for Cancer Theranostics

2017-08-17T20:25:51+00:00August 17th, 2017|Categories: Publications|Tags: |

Multifunctional biodegradable inorganic theranostic nano-agents are of great interests to the field of nanomedicine. Herein, VS2 nanosheets upon lipid modification could be converted into ultra-small VS2 nanodots encapsulated inside polyethylene glycol (PEG) modified lipid micelles. Owing to the paramagnetic property, high near-infrared (NIR) absorbance, and chelator-free 99mTc4+ labeling of VS2, such [email protected] nanoparticles could be used for T1-weighted magnetic resonance (MR), photoacoustic (PA),and single photon emission computed tomography (SPECT) tri-modal imaging guided photothermal ablation of tumors. Importantly, along with the gradual degradation of VS2, our [email protected] nanoparticles exhibit effective body excretion without appreciable toxicity. Our work presents the unique advantages of VS2 nanostructures with highly integrated functionalities and biodegradable behaviors, promising for applications in cancer theranostics.

Published in: "Angewandte Chemie International Edition".

Modulation of Metal and Insulator States in 2D Ferromagnetic VS2 by van der Waals Interaction Engineering

2017-08-01T16:30:17+00:00August 1st, 2017|Categories: Publications|Tags: |

2D transition-metal dichalcogenides (TMDCs) are currently the key to the development of nanoelectronics. However, TMDCs are predominantly nonmagnetic, greatly hindering the advancement of their spintronic applications. Here, an experimental realization of intrinsic magnetic ordering in a pristine TMDC lattice is reported, bringing a new class of ferromagnetic semiconductors among TMDCs. Through van der Waals (vdW) interaction engineering of 2D vanadium disulfide (VS2), dual regulation of spin properties and bandgap brings about intrinsic ferromagnetism along with a small bandgap, unravelling the decisive role of vdW gaps in determining the electronic states in 2D VS2. An overall control of the electronic states of VS2 is also demonstrated: bond-enlarging triggering a metal-to-semiconductor electronic transition and bond-compression inducing metallization in 2D VS2. The pristine VS2 lattice thus provides a new platform for precise manipulation of both charge and spin degrees of freedom in 2D TMDCs availing spintronic applications. Van der Waals interaction engineering in VS2 brings the first intrinsic ferromagnetic semiconductor in 2D transition-metal dichalcogenides (TMDCs). An experimental realization of intrinsic magnetic ordering in a pristine TMDC lattice is reported. The pristine VS2 lattice provides a new platform for precise manipulation of both charge and spin degrees of freedom in 2D TMDCs, availing spintronic applications.

Published in: "Advanced Materials".

Hierarchical VS2 Nanosheet Assemblies: A Universal Host Material for the Reversible Storage of Alkali Metal Ions

2017-07-17T08:29:25+00:00July 17th, 2017|Categories: Publications|Tags: , |

Reversible electrochemical storage of alkali metal ions is the basis of many secondary batteries. Over years, various electrode materials are developed and optimized for a specific type of alkali metal ions (Li+, Na+, or K+), yet there are very few (if not none) candidates that can serve as a universal host material for all of them. Herein, a facile solvothermal method is developed to prepare VS2 nanosheet assemblies. Individual nanosheets are featured with a few atomic layer thickness, and they are hierarchically arranged with minimized stacking. Electrochemical measurements show that VS2 nanosheet assemblies enable the rapid and durable storage of Li+, Na+, or K+ ions. Most remarkably, the large reversible specific capacity and great cycling stability observed for both Na+ and K+ are extraordinary and superior to most existing electrode materials. The experimental results of this study are further supported by density functional theory calculations showing that the layered structure of VS2 has large adsorption energy and low diffusion barriers for the intercalation of alkali metal ions.

Thumbnail image of graphical abstract

Hierarchical VS2 nanosheet assemblies featuring a few atomic-layer nanosheet thickness are prepared by a facile solvothermal method in N-methyl-2-pyrrolidone. They can serve as a universal host material for the reversible electrochemical storage of Li+, Na+, or K+ ions with large capacity, great rate capability, and satisfactory cycling stability.

Published in: "Advanced Materials".

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