In this 2D NiCo-MOF/rGO hybrid, the MOF nanosheets provide abundant active sites while the conductive rGO provide rapid electron transport.

Three-dimensional (3D) core/shell structure of nickel cobalt sulfide is nano-engineered by using series of hydrothermal steps on a CVD grown graphene for supercapacitor application. This core/shell is composited of NiCo2S4 nanotube (NCS) as core and CoxNi(3−x)S2 (CNS) nanosheets as a shell. The as-synthesized composite exhibits excellent electrochemical properties by using the advantage of NCS nanontube core as superhighway for electron and ion transport, and CNS nanosheets shell as high active area pseudocapacitive material. The 3D graphene layer serves as excellent surface area to support 3D NCS/CNS; moreover, it provides excellent electrical conductivity between nickel foam current collector and the 3D NCS/NCS composite. Using these hybrid advantages the as-synthesized graphene/NCS/CNS composite electrode exhibits high areal capacitance of 15.6 F/cm2 at current density of 10 mA/cm2; excellent cycling stability of 93% after 5000 of cycles and excellent rate capability of 74.36% as current increase from 10 to 100 mA/cm2. Moreover, a prototype of asymmetric device fabricated using graphene/NCS/CNS as positive electrode and RGO as negative electrode exhibits high energy density of 23.9 Wh/kg and power density of 2460.6 W/kg at high operating current of 100 mA. Such high performance electrode material may get great application in future energy storage device.

Photoinduced hysteresis (PIH) of graphene field-effect transistors (G-FETs) has attracted attention because of its potential in developing photoelectronic or nonvolatile memory devices. In this work, we focused on the role of SiO 2 dielectric layer on PIH, where G-FETs have only a SiO 2 dielectric layer. Adsorbates are effectively removed before the PIH test. The effects of laser wavelength, laser power density, and temperature on the PIH are systematically investigated. The PIH is significantly enhanced by increasing the hydrogen flow in a hydrogen-atmosphere device thermal annealing. This strongly suggests proton-related defects that play a key role. The pure electronic process for PIH is further ruled out by the significant dependence of the doping rate on the temperature. A mechanism of PIH based on proton generation after hole trapping at [O 3 Si−H] is proposed. The proposed mechanism is well-supported by our experimental data: (1) the observed threshold photon energy for PIH is between 2.76 and 2.34 eV, which is close to the energy barrier for [O 3 Si−H], releasing a proton. (2) No obvious carrier mobility degradation after the PIH process suggests that the bulk defects in SiO 2 are the major contributors rather than graphene/SiO 2 interface defects. (3) The dependence of the doping rate on the temperature and the laser power density matches a theoretical model based on the random hopping of H + . The results in this work are also valuable for the study of degradation of other oxide dielectric materials in various field-effect transistors.

The unique porosity derived from sulphur templates enables easy diffusion of electrolyte ions and improved electrochemical performance is obtained.

Urchin-like NiCo2S4 hexagonal pyramid microstructures have been successfully fabricated on 3-D graphene nickel foam by a two-step hydrothermal method. These achieve a rather high mass loading, with enhanced specific capacitance, rate performance and cycling stability.

Cockscomb flower-like NiCo 2 S 4 composite material is made for supercapacitor application by using two step hydrothermal processes. The cockscomb flowerlike NiCo 2 S 4 architecture contains numerous ultrathin folded nanosheets which increases the active areas of the electrode and the three dimensional open space between the flower sheets facilitates the easy flow of electrolyte ions and leads to efficient utilization of active materials even at high current densities. Two kinds of composite electrodes were fabricated by coating and in situ growing a cockscomb flower-like of NiCo 2 S 4 on nickel foam current collector. The in situ grown cockscomb flower-like NiCo 2 S 4 showed superior performance compared to cockscomb flower-like of NiCo 2 S 4 coated on nickel foam by avoiding the uses of polymer binders which adds dead areas and increase resistance on the electron and ion diffusion. Using this advantage the in situ grown cockscomb flower-like of NiCo 2 S 4 showed high specific capacitance of 1707 F/g at current density of 1 A/g and areal capacitance of 4.1 F/cm 2 at current density of 2.4 mA/cm 2 with good rate capability of 65.12 % as current increases from 2.4 to 80 mA/cm 2 . Such excellent conductive and stable structure may find potential application in future energy storage devices.

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