Query: VO2 (M)

title: A durable VO2(M)/Zn battery with ultrahigh rate capability enabled by pseudocapacitive proton insertion
abstract: Energy storage devices with low cost and high safety features are essential because of the continued consumption of fossil fuels. Aqueous zinc ion batteries, owing to their superior safety, high abundance and high theoretic capacity, have attracted increasing attention. Herein, for the first time, the M phase VO2 integrated with carbon nanotubes as a binder free cathode for zinc ion batteries was studied. The as prepared binder free cathode shows ultrahigh rate performance with 248 mA h g 1 at 2 A g 1, 232.6 mA h g 1 (93.8% maintained compared to 2 A g 1) at 20 A g 1 and 194.9 mA h g 1 at 40 A g 1. Good stability was achieved with 84.5% retention after up to 5000 cycles at 20 A g 1. This ultrahigh capacity retention at such high current densities is comparable among the reported studies. To fundamentally reveal the electrochemical mechanism, the bond valence method was employed to unravel the migration pathway of H+/Zn2+ in VO2(M) The H+ diffusion pathway was fluent, while the Zn2+ route had a narrow and blocked passage, which was consistent with the reversible deposition/dissolution of hydroxyzinc sulfate hydrate in the electrochemical process. The pseudocapacitive proton insertion mechanism can be a promising strategy to explore cathode materials for aqueous zinc ion batteries.

title: Surfactant mediated prepared VO2 (M) nanoparticles for efficient solar steam generation
abstract: Herein, for the first time, we demonstrated the potential practicability of VO2 (M) as a low cost and stable photoabsorber coated on a piece of poplar wood (W/S8 M) in solar steam generation of Caspian Sea water. The evaporation rate of 3.63 kg m 2 h 1 and the solar steam generation efficiency of 75.60% for W/S8 M were obtained under 3 sun (3 kW m 2) irradiation within 40 min. The concentration of sodium ions in the seawater decreased from 3138.19 to 6.61 mg L 1 for W/S8 M which is far below the drinking water standards. The pH and electrical conductivity of seawater was decreased after desalination by W/S8 M to a large extent. A surfactant mediated method using different amounts of cetyltrimethylammonium bromide (CTAB) was used to prepare VO2 (M) It was revealed that the sample prepared by addition of 0.08 g CTAB using hydrothermal method has the smallest particle size of 230 nm, the largest specific surface area of 14.542 m2 g 1, the greatest mean pore size of 43.53 nm, narrow thermal hysteresis width of 4.12 degC, and the lowest semiconductor metal phase transition temperature of 65.23 degC. For the first time, the ATR FTIR spectroscopy was used to monitor the SMT of VO2 (M) at different temperatures. We found that the samples have the same unique ATR FTIR spectra below Tc with the characteristic band at 835 and a shoulder at 1020 cm 1 while at T Tc, the fairly linear curves without any meaningful band are appeared.

title: VO2(M) nanoparticles with controllable phase transition and high nanothermochromic performance
abstract: VO2 has been intensively studied because of its metal insulator transition. Based on the metal insulator transition, smart thermochromic coating is made to regulate the solar transmittance of windows. In this paper, VO2(M) nanoparticles (NPs) were prepared by a mild annealing treatment of orthorhombic VOOH. The size, morphology, phase transition temperature and hysteresis of VO2(M) can be tailored by adjusting annealing conditions. It was found that the particle size and crystallinity play vital roles in determining the thermochromic performance of VO2(M) NPs films, and an optimal luminous transmittance Tlum of about 48.8% and a solar regulation efficiency DTsol of about 14.9% can be achieved. The mild annealing conditions and controllable transformation from VOOH to VO2(M) provide a new way to regulate the size and morphology of VO2(M) NPs, which is essential in studying the nature of phase transition and improving the thermochromic performance.

title: Facile synthesis of VO2 (D) and its transformation to VO2(M) with enhanced thermochromic properties for smart windows
abstract: Pure VO2(M) is usually synthesised by the hydrothermal method and a subsequent annealing process at high temperatures >400 degC) However, the high temperature annealing process always leads to large sized VO2(M) particles without reduced phase transition temperature. In this work, VO2(D) spherical particles composed of nanotablets were synthesised by the hydrothermal process and then converted into VO2(M) nanoparticles by annealing at 250 400 degC for 0.5 5 h. The obtained VO2(M) grains exhibited a grain size of 20 30 nm and a reduced phase transition temperature of ~62 degC compared with that of bulk M VO2 ~68 degC) With an increase in the annealing temperature from 250 degC to 400 degC, the grain size increased from 20 nm to 30 nm, the phase transition temperature increased slightly from 62.17 degC to 62.70 degC, and the hysteresis width increased from 5.72 degC to 7.51 degC. This was possibly attributable to the grain size effect and the interface effect. In addition, the VO2(M) nanoparticle based film showed an initial increase and then a decrease in the visible transmittance (Tlum) and solar modulation efficiency (DTsol) When the annealing time was extended from 0.5 h to 5 h, Tlum of the VO2(M) nanoparticle based film is firstly increased and then decreased while DTsol is increased from 5.74% to 11.90% Therefore, this work provides a facile way to synthesise pure VO2(M) nanoparticles with reduced phase transition temperature and enhanced thermochromic performance.

title: Polycrystalline VO2(M) with well dispersed crystalline zones for enhanced electroactivity of lithium ion batteries
abstract: Constructing polycrystalline structure is an effective strategy to improve the electrochemical performance of electrode materials. To enhance the electroactivity of anisotropic VO2(M) polycrystalline VO2(M) with well dispersed crystalline zones is successfully synthesized by a facile one step hydrothermal method, and then their electrochemical performances as an anode of lithium ion batteries are systematically explored. Results show that the synergistic effect of crystalline zones and amorphous matrices in polycrystalline structure can dramatically activate the anisotropic VO2(M) electrode, which contributes to increasing the electroactive zones and facilitating the charge transfer kinetics. Compared with single crystal VO2(M) polycrystalline VO2(M) shows the significantly enhanced electrochemical performance, delivering a high reversible capacity of 476 mAhg 1 at 100 mAg 1 after 150 cycles, which is far superior to the theoretical capacity and the reported mixture of VO2(M) and VO2(B) This work opens up new insights for the activation of anisotropic electrode materials.

title: Pt free, low cost and efficient counter electrode with carbon wrapped VO2(M) nanofiber for dye sensitized solar cells
abstract: The present study reports the use of one dimensional carbon wrapped VO2(M) nanofiber (VO2(M)/C) as a cost effective counter electrode for dye sensitized solar cells (DSSCs) where M denotes monoclinic crystal system. Uniform short length nanofiber was synthesised by a sol gel based simple and versatile electrospinning and post carbonization technique. The investigation of nanostructure and morphological analysis were performed by X ray diffraction (XRD) field emission scanning electron microscope (FE SEM) and transmission electron microscope (TEM) with EDAX. The electrochemical response was comprehensively characterized by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization. The electrochemical analysis of the VO2(M)/C nanofiber counter electrode exhibits significant electrocatalytic activity towards the reduction of triiodide and low charge transfer resistance at the electrode electrolyte interface. The DSSCs fabricated with carbon wrapped VO2(M) nanofiber CE showed high power conversion efficiency of 6.53% under standard test condition of simulated 1SUN illumination at AM1.5 G, which was comparable to the 7.39% observed for conventional thermally decomposed Pt CE based DSSC under same test conditions. This result encourages the next step of modification and use of low cost VO2(M) as an alternate counter electrode for DSSCs to achieve a substantial efficiency for future energy demand.

title: Preparation and microwave absorption properties of microsheets VO2(M)
abstract: Microsheets structural VO2(M) was prepared by a hydrothermal and subsequent annealing method in this work. After a system characterization, it is found that VO2(M) microsheets obtained by annealing method at 570 degC has a minimum RL value of 45.8 dB and a maximum effective absorption bandwidth (RL

title: Size Dependent Crystal Transition Thermodynamics of Nano VO2 (M)
abstract: Vanadium dioxide exhibits a reversible crystal transition from monoclinic phase to rutile phase, but the quantitative regularity of the effect of particle size on crystal transition thermodynamics

title: Thermal hysteresis control of VO2 (M) nanoparticles by Ti F codoping
abstract: We have synthesized F doped Ti x V 1 x O2 nanoparticles by hydrothermal method and examined the structural phase transition behavior depending on the Ti and F contents. Differential scanning calorimetry and temperature dependent X ray diffraction analyses revealed that, by the codoping of Ti and F in VO2, both the critical phase transition temperature (Tc) and the thermal hysteresis width D T c are appropriately reduced. We have also examined the thermochromic behavior for the composite films prepared by casting F doped Ti x V 1 x O2 nanoparticles. The 2.0% F doped Ti 0.08 V 0.92 O2 composite film exhibited a decreased Tc of approximately 20 degC and narrow D T c of below 2 degC. This result clearly shows the potential of F doped Ti x V 1 x O2 nanoparticles for sensitive optical device application.

title: VO2(A) nanorods: One pot synthesis, formation mechanism and thermal transformation to VO2(M)
abstract: The monoclinic VO2(M) has promising applications in intelligent devices but its preparation still requires improvement to permit cost effective mass production. In this work, we report a 2 stage approach for producing VO2(M) nanorods by (1) hydrothermal reduction of vanadium pentoxide by sodium bisulfate at 220 degC to form VO2(A) and (2) subsequent thermal activated phase transformation of VO2(A) to VO2(M) at 350 450 degC in vacuum. The obtained VO2(M) nanorods showed a reversible phase transition temperature at about 62.5 degC and a narrow thermal hysteresis width of 10 degC. The mechanism of the hydrothermal reduction was studied by combined ex situ microscopic and diffraction characterization of cooled samples as well as in situ PXRD experiments, in which the hydrothermal synthesis was monitored in real time by time resolved diffraction datasets. It was found that the hydrothermal synthesis of VO2(A) is a 4 step process: (1) reduction of V2O5 to form VO2(B) nanoparticles, (2) oriented attachment of VO2(B) nanoparticles along the [110] direction, (3) formation of VO2(B) nanorods as a results of oriented attachments, and (4) hydrothermal transformation of the metastable intermediate VO2(B) nanorods to VO2(A) nanorods. This clear understanding of the mechanism will help the further optimization of synthesis temperature and time for preparing VO2(A) This method provides a low temperature thermal treatment alternative and hence helps the reduction of cost for the production of VO2(M) bring the mass application of VO2(M) one step closer.