Ziqing Zhang

Facile synthesis of hierarchical CoMoO4@NiMoO4 core–shell nanosheet arrays on nickel foam as an advanced electrode for asymmetric supercapacitors

Hierarchical CoMoO4@NiMoO4 core–shell nanosheet arrays were successfully grown on nickel foam via a facile two-step hydrothermal method followed by calcination treatment. With an ordered core–shell nanostructure and a desired composition, the optimized CoMoO4@NiMoO4 composite electrode exhibited a high specific capacitance of 1639.8 F g−1 (3.30 F cm−2) and an excellent cycling stability with a 95% retention rate at a high current density of 20 mA cm−2 after 3000 cycles. Additionally, an asymmetric supercapacitor (ASC) was assembled with CoMoO4@NiMoO4 nanosheet arrays/Ni foam as the positive electrode and activated carbon (AC) as the negative electrode, which displayed an energy density of 28.7 W h kg−1 at a power density of 267 W kg−1. The remarkable electrochemical performance indicated that the CoMoO4@NiMoO4 composite was a promising electrode material and had great application potential for energy storage.

One-step synthesis of hierarchical ZnCo2O4@ZnCo2O4 core–shell nanosheet arrays on nickel foam for electrochemical capacitors

An integrated electrode of hierarchical ZnCo2O4@ZnCo2O4 core–shell nanosheet arrays/nickel foam has been successfully synthesized, via a one-step hydrothermal method followed by calcination treatment. The hierarchical ZnCo2O4@ZnCo2O4 nanosheet arrays seem to possess mesoporous characteristics with ultrathin thickness. Due to its novel, hybrid nanoarchitecture, such an electrode system has exhibited remarkable areal specific capacitance along with excellent cycling life, even under fairly high current density conditions.

Synthesis and characterization of multipod frameworks of Cu2O microcrystals and Cu7S4 hollow microcages

A variety of multipod frameworks of Cu2O microcrystals have been prepared through careful control of the ratios of n-butyl alcohol to water, and novel 14-pod Cu2O frameworks are first reported. Moreover, template-assisted synthesis of multipod frameworks of Cu7S4 microcages using the obtained Cu2O microcrystals as sacrificial templates is reported.

The synthesis of hierarchical ZnCo2O4@MnO2 core–shell nanosheet arrays on Ni foam for high-performance all-solid-state asymmetric supercapacitors

Hierarchical ZnCo2O4@MnO2 core–shell nanosheet arrays were successfully synthesized on Ni foam via a facile hydrothermal method followed by a calcination process. The fabricated ZnCo2O4@MnO2 electrode exhibited a specific capacitance as high as 2170.00 F g−1 (2.60 F cm−2) at a current density of 3 mA cm−2 in a 1 M KOH solution. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) device fabricated with the as-prepared ZnCo2O4@MnO2 as the positive electrode and activated carbon (AC) as the negative electrode in the PVA/KOH gel electrolyte achieved a high energy density of 29.41 W h kg−1 at a power density of 628.42 W kg−1 and retained 95.3% of its initial capacitance after 3000 cycles at a high current density of 10 mA cm−2. With the smart design and remarkable electrochemical properties, the hierarchical ZnCo2O4@MnO2 core–shell nanosheet arrays on Ni foam demonstrated great potential for further applications in the energy storage field.

Synthesis of perovskite-type manganites Yb1−xDyxMnO3 (0.1 ≤ x ≤ 0.5) via solid-state reaction and high-pressure flux methods followed by structural characterization and magnetic property studies

A series of hexagonal perovskite-type compounds Yb1−xDyxMnO3 (0.1 ≤ x ≤ 0.5) have been prepared by the traditional solid-state reaction method at 1573 K, and a single crystal orthorhombic perovskite-type compound Yb0.5Dy0.5MnO3 has also been obtained by a high-pressure flux method at 1273 K under 5 GPa high pressure. Final products are fully characterized by XRD and XPS analyses, and then subject to magnetic measurements. It appears that the hexagonal Yb1−xDyxMnO3 (0.1 ≤ x ≤ 0.5) compounds have shown antiferromagnetic properties with a Neel temperature of 10 K, and canted antiferromagnetic behaviour is clearly evident at a lower temperature. Also, it is found that the magnetization of Yb1−xDyxMnO3 increases with the increase of Dy content. The orthorhombic Yb0.5Dy0.5MnO3 single crystal has been found to be paramagnetic, differing from RMnO3 reported in the literature, which is antiferromagnetic due to subtle structural difference.

A facile one-step hydrothermal approach to synthesize hierarchical core–shell NiFe2O4@NiFe2O4 nanosheet arrays on Ni foam with large specific capacitance for supercapacitors

In this contribution, NiFe2O4@NiFe2O4 nanosheet arrays (NSAs) with three-dimensional (3D) hierarchical core–shell structures were synthesized by a facile one-step hydrothermal method and they were used as electrode materials for supercapacitors (SCs). The NiFe2O4@NiFe2O4 composite electrode showed a high specific capacitance of 1452.6 F g−1 (5 mA cm−2). It also exhibited a superior cycling stability (93% retention after 3000 cycles). Moreover, an asymmetric supercapacitor (ASC) was constructed utilizing NiFe2O4@NiFe2O4 NSAs and activated carbon (AC) as the positive and negative electrode, respectively. The optimized ASC shows extraordinary performances with a high energy density of 33.6 W h kg−1 at a power density of 367.3 W kg−1 and an excellent cycling stability of 95.3% capacitance retention over 3000 cycles. Therefore, NiFe2O4@NiFe2O4 NSAs have excellent pseudocapacitance properties and are good electrode materials for high energy density.

Pressure quenching: a new route for the synthesis of black phosphorus

Methods to synthesize black phosphorus (BP) have been studied over the last few decades with several challenges remaining to be solved. In this paper, BP flakes were synthesized using a novel method, which we named as “Pressure Quenching” approach. Briefly, BP was obtained from red phosphorus (RP) through a controllable phase transition under conditions below 0.4 GPa and 580 °C. The mechanism was investigated in detail via a decompression process at fixed temperature with the phase transition exhibiting an energy barrier dependence. Meanwhile, an extra tunable energy was generated by pressure quenching as a supplement for the phase transition. Therefore, the transition from RP to BP could be easily controlled by tuning the applied pressure.

One-Step Controllable Synthesis of Mesoporous MgCo2O4 Nanosheet Arrays with Ethanol on Nickel Foam as an Advanced Electrode Material for High-Performance Supercapacitors

In recent years, ternary transition metal oxides (TTMOs), especially spinel type TTMOs have attracted widespread attention as promising candidates for electrode materials. Among all of the popular TTMOs, MgCo2 O4 is an outstanding one, owing to its superior theoretical capacitance. In this work, MgCo2 O4 nanosheet arrays (NSAs) grown directly on nickel foams were fabricated through a facile hydrothermal process at 120 °C for 4 h. With a series of structural and morphological characterization techniques, it was found that the ethanol played a key role in controlling the composition and morphology during the synthesis process. The MgCo2 O4 NSAs exhibited a superior specific capacitance of 853.06 C g-1 (at 1 mA cm-2 ) and enhanced cycling performance, with 94.65 % of initial capacitance retained after 3000 cycles when used as a binder-free integrated electrode for electrochemical supercapacitors; much higher than other reported data for MgCo2 O4 as well. The excellent electrochemical properties mainly came from the unique morphology of the MgCo2 O4 NSAs. This study will demonstrate the applications of MgCo2 O4 NSAs based large-scale supercapacitors grown on low-cost nickel foams.

Acetic Acid Assistant Hydrogenation of Graphene Sheets with Ferromagnetism

Ferromagnetism of pure carbon-based materials has been widely researched for several years. In therocially and experimentally, semi-hydrogenation graphene sheets exhibit ferromagnitism, which is related to the degree of hydrogenation. Here we reported the controllable hydrogenation of graphene using ball-milling method with acetic acid as hydrogenating agent. The hydrogenation graphene sheets were characterized by means of transmission electron microscopy(TEM), Raman spectroscopy and X-ray photoelectron spectroscopy, and magnetic measurement. The relusts of Raman spectroscopy demonstrate that the relative intensity of D band increases with the hydrogenation degree. The resluts of magnetic meansurement indicate the maximal magnetic moment of 0.274 A·m2/kg at 2 K for semi-hydrogenation graphene.

Heterostructural MnO2@NiS2/Ni(OH)2 materials for high-performance pseudocapacitor electrodes

A new MnO2@NiS2/Ni(OH)2 heterostructure material was synthesized using a two-step hydrothermal process. The presence of 1D MnO2 nanosticks provided a substrate for the junction and facilitated the charge transmission. The grafting of NiS2/Ni(OH)2 sheets onto the surface of MnO2 enlarged the specific surface area (SSA) of the material. As a result, the SSA of the electrode material was improved and the capacitor performance was optimized. The material also showed a high rate capacity and long-term cycling capability.