Jiandong Wu

When Cubic Cobalt Sulfide Meets Layered Molybdenum Disulfide: A Core–Shell System Toward Synergetic Electrocatalytic Water Splitting

A new class of Co9 S8 @MoS2 core-shell structures formed on carbon nanofibers composed of cubic Co9 S8 as cores and layered MoS2 as shells is described. The core-shell design of these nanostructures allows the advantages of MoS2 and Co9 S8 to be combined, serving as a bifunctional electrocatalyst for H2 and O2 evolution.

Multiwalled carbon nanotubes–V2O5 integrated composite with nanosized architecture as a cathode material for high performance lithium ion batteries

Multiwalled carbon nanotubes (MWCNTs)–V2O5 integrated composite with nanosized architecture has been synthesized through hydrothermal treatment combined with a post-sintering process. During the hydrothermal reaction, protonated hexadecylamine (C16H33NH3+) acts as an intermediator, which links the negatively charged vanadium oxide layer with the mixed-acid pretreated MWCNTs by weak electrostatic forces to form a three-phase hybrid (MWCNTs–C16–VOx). MWCNT–V2O5 composite and V2O5 nanoparticles can be obtained by sintering MWCNTs–C16–VOx at 400 and 550 °C in air, respectively. Among them, MWCNTs–V2O5 possesses better electrochemical performance as a cathode material for lithium ion batteries (LIBs). The unique porous nanoarchitecture of MWCNTs–V2O5 provides a large specific surface area and a good conductive network, which facilitates fast lithium ion diffusion and electron transfer. Additionally, the uniformly dispersed MWCNTs conducting network also behaves as an effective buffer which can relax the strain generated during charge–discharge cycles. Electrochemical tests reveal that MWCNTs–V2O5 could deliver a superior specific capacity (402 mA h g−1 during initial discharge at a current density of 100 mA g−1 between 1.5 and 4 V versus Li/Li+), good cycling stability (222 mA h g−1 after 50 cycles) and high rate capability (194 mA h g−1 at a current density of 800 mA g−1).

MgVPO4F as a one-dimensional Mg-ion conductor for Mg ion battery positive electrode: a first principles calculation

MgVPO4F is proposed as a cathode material for rechargeable Mg ion batteries for the first time. First principles calculations were performed to study the electrochemical properties of MgVPO4F as a positive electrode material for rechargeable Mg ion batteries. Our theoretical study gives an expectation of good battery performance by MgVPO4F.

A new method to prepare vanadium oxide nano-urchins as a cathode for lithium ion batteries

Urchin-like vanadium oxide nanotube clusters, abbreviated to VOx-NUs, were synthesized using a new method. Vanadium pentoxide, having a layered structure, was modified by lithium fluoride (LiF) and transformed into bi-phase lithium vanadate as the inorganic precursor. Then, VOx-NUs were prepared by hydrothermal reaction with dodecylamine as a template. This is different from other molecular assembly methods reported. VOx-NUs-350 nano clusters were obtained by annealing VOx-NUs at a temperature of 350 °C in air. Both samples were identified as three dimensional urchin-like nano clusters. Based on the characterization data obtained, a formation mechanism was established. By simply varying the LiF stoichiometric ratio, the nano tube density of the VOx-NUs could be controlled. VOx-NUs presented a higher initial rate capacity of 400 mA h g−1 and VOx-NUs-350 maintained a better capacity of 150 mA h g−1 after 50 cycles at a 100 mA g−1 current density between 1.5 and 4 V versus Li/Li+.

A facile method to prepare bi-phase lithium vanadate as cathode materials for Li-ion batteries

Bi-crystal lithium vanadate is synthesized with starting materials of V2O5 and LiF by one-step solid-state reaction. Since fluorine reacts with crucible made of silica, Li0.3V2O5-liked and LiV3O8-liked phases without F coexist in the produces. The stoichiometric proportion of two phases depends on the amount of dopant LiF. These are confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and transmission electron microscopy (TEM). Charge and discharge curves of bi-crystal materials present better reversibility of voltage plateaus than that of pure V2O5. The initial discharge capacity of Li0.3V2O5-liked phase dominated bi-crystal material is higher than pure V2O5. LiV3O8-liked phase dominated bi-crystal material has lower initial discharge capacity but delivers better cycling performance. Electrochemical impedance spectroscopy (EIS) measurements are performed to evaluate electrochemical kinetics of the bi-crystal materials. The results indicate that bi-crystal phase benefit the transfer resistance, interior diffusion resistance, and structure stability. Cathodes with different bi-phase structures have variable charge transfer resistance and lithium-ion diffusion speed due to this special structure.

Influence of MoO3 addition on the gasochromism of WO3 thin films

Pure tungsten oxide thin films apparently show gasochromic performance, based on PdCl2 catalyst. In this paper, adulteration of MoO3 into WO3 sol has been achieved via sol-gel method. FT-IR, Differential Scanning Calorimeter (DSC-TG) and Uv-visible Spectroscopy have been used to analysis the compound sols, films and optical properties for the use of this material as smart windows. FT-IR shows that for the compound, new characteristic absorption bands arise, which is different from pure WO3 or MoO3. DSC-TG shows the phase change during the temperature ascending from 50 to 800°C. The compound thin films performs relatively well in coloring response time, colored extent, coloring-bleaching recycling and gasochromic effect with non-unicity color.

Effect of UV and vacuum treatment on stability of WO3 gas sensing films

UV and vacuum treatment, as well as annealing, were tried to recover the gas sensing property of WO3 films. Results show that gas sensing films can partially recover one or two coloring and bleaching cycles if kept in vacuum condition. And UV irradiation can well recover several cycles. But heat treatment does not show any obvious effect on the gas sensing recovery. Furthermore, IR and XPS spectra were used to identify the mechanism of this improvement. Results reveal that changes of water content will reduce the desorption energy of hydrogen atom, which will accelerate the bleaching velocity.