•Hierarchical structured layered-double-hydroxides derived by ZIF-67 was successfully synthesized and characterized.•The adsorption tests for both high and trace concentrations of uranium (VI) were conducted in details.•Mg-Co LDHs derived by ZIF-67 possesses high adsorption capacity and selectivity for uranium (VI).Under the background of increasing and sustainable development of nuclear industry, it is significant to develop materials with high adsorption capacity and high selectivity of uranium as adsorbents. In this work, novel Mg-Co layered-double-hydroxide (LDH) with hierarchical structure was synthesized successfully via self-sacrifice template by ZIF-67. X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller surface area measurement (BET) and X-ray photoelectron spectroscopy (XPS) characterization were conducted, which confirmed the specifically hollow structured material possesses high surface area and abundant mesopores that makes uranium ions diffuse into it more easily. In typical batch adsorption experiments, varieties of parameters were investigated in details. In addition, adsorption of trace concentration of uranium (ppb level) in simulated seawater was also studied. The results showed as-prepared Mg-Co LDHs are promising adsorbents for extraction of uranium from simulated seawater.Download high-res image (178KB)Download full-size image

⿢3D Flower-like Co3O4 nanosheet networks was synthesized.⿢Co3O4/PPy electrode is binder- and conductive additives-free.⿢Co3O4/PPy nanocomposite electrode shows high areal capacitance.3D flower-like Co3O4/Polypyrrole (PPy) nanosheet networks are directly grown onto Ni foam involving the solution-based method and in-situ oxidative polymerization of pyrrole for supercapacitor electrode materials. The as-prepared electrode takes advantage of the exceptional architecture of Co3O4 and high electronic conductivity of PPy. Electrochemical measurements show that the areal capacitance of 3D Co3O4/PPy electrode is 6.81 F cm⿿2 at 5 mA cm⿿2 in 6 mol L⿿1 KOH aqueous solution. The capacitance is 95% of original capacitance after 1000 cycles at 20 mA cm⿿2. With superior electrochemical characteristics and the ease of large scale fabrication, the 3D flower-like Co3O4/Polypyrrole nanosheet networks provide promising electrode material for supercapacitor applications.3D interconnected flower-like Co3O4 nanosheet networks onto Ni foam using a simple solution-based method and following annealing process. PPy was further fixed on Co3O4 nanosheet networks array by oxidative polymerization of pyrrole.Download high-res image (146KB)Download full-size image

Some inorganic quasi-two-dimensional nanomaterials such as cobalt–nickel hydroxides are kinetically facile for a capacitive charge storage process. However, high performance capacitive charge storage needs a balance of the ionic and electronic transporting, and to build up an integrated architecture on substrates step by step and utilize the interface better is still a key challenge. As the interfacial assembly has conflicted with our goals for high-performance capacitive charge storage process, we identify theoretically and experimentally binary cooperative nanoscale interfacial materials to solve the problem. Co–Ni-hydroxide precursors were prepared by hybrid quasi-two-dimensional nanosheets and hetero-oriented nanocrystallines walls. Followed by dip-dry and annealing, NiCo2O4 could adhere to the nickel foams robustly with a solution-based surface treatment. Moreover, an unusual phenomenon in the electrochemical test inspired us to establish a bridge between ‘supercapacitor’ and ‘battery’. The bridged gap highlights a new design idea for high-performance energy storage.

V2O5/Ketjin black (VK) nanocomposites with mesoporous mica-like structure were prepared by a facile sol–gel method. Through a dip–dry process, the VK nanocomposites were successfully assembled on nickel foams with controllable mass loadings. The as-prepared electrode (VK2) shows high areal capacitance (3.9506 F cm−2 at 5 mA cm−2) and good cycling stability (90% after 8000 cycles) in a LiCl/PVA gel electrolyte. Furthermore, the VK nanocomposite-based all-solid-state symmetric supercapacitor can provide a maximum energy density of 56.83 W h kg−1. Such excellent electrochemical performance may promote the VK nanocomposites as promising electrode materials for practical applications.

3D interconnected NiCo2S4 nanosheets have been directly grown on nickel foams using a facile two-step solution-based method. The as-prepared electrodes with controllable mass loadings and microstructures show excellent electrochemical performance, indicating their potential application as supercapacitors. Electrochemical measurements exhibit that the NiCo2S4/nickel foam electrode has a competitive areal specific capacitance (10.82 F cm−2 at 10 mA cm−2), relatively high rate capability (40.3% capacitance retention at 80 mA cm−2) and good cycling stability (92% capacitance retention after 1500 cycles at 20 mA cm−2).

Hierarchical NiO nanospheres composed of porous nanosheets are prepared by a facile trisodium citrate assisted precipitation route followed by a calcination process. Effects of the trisodium citrate on the microstructure and electrochemical performances of NiO nanospheres are systematically investigated. The XRD, SEM, TEM, BET, and TG analyses show that the key point of the successful realization is that the citrate positioned in the precursor α-Ni(OH)2 layer, which can prevent the restacking of α-Ni(OH)2 sheets, yielding better crystallinity, high surface area (182 m2 g−1) as well as pore volume (0.15 cm3 g−1) and hierarchical porous ball-like morphology of NiO nanospheres by the calcination of the precursor. Electrochemical results show that the hierarchically porous NiO obtained with trisodium citrate assisted route exhibits high rate charge–discharge performance (463 F g−1 at 4.5 A g−1), longer cyclic stability (95% capacitance remained after 1000 charge–discharge cycles at 0.5 A g−1) as compared to the NiO prepared in the absence of sodium citrate (182 F g−1 at 4.5 A g−1; 70% capacitance retention after 1000 charge–discharge cycles at 0.5 A g−1). Further, due to facile mass transfer in the perfectly porous nanosheet, the citrate-assisted NiO show lower equivalent series resistance as revealed from the impedance studies.Graphical abstractHierarchical NiO microspheres composed of porous nanosheets were prepared by a facile trisodium citrate assisted precipitation route followed by a calcination process. The sodium citrate assisted obtained NiO has high specific surface area, large pore volume, and narrow pore size distribution. Significantly, compared with the ordinary NiO, the unique hierarchical NiO spheres showed a remarkable discharge capacity and electrochemical stability due to the unique morphology and pore size distribution. Highlights► NiO samples were synthesized using a facile trisodium citrate assisted route. ► Citrate positioned in the precursor interlayer to control the morphology and size. ► Citrate-assisted NiO showed higher specific capacitance and lower ESR. ► Citrate-assisted NiO exhibited good cycling stability and capacitance retention.

NiO nanofibers modified by citric acid (NiO/CA) for supercapacitor material have been fabricated by electrospinning process. The characterizations of the nanofibers are investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical properties are characterized by cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy. Results show that the NiO/CA nanofibers are hollow tube and comprised of many NiO sheets. Furthermore, the NiO/CA nanofibers have good electrochemical reversibility and display superior capacitive performance with large capacitance (336 F g−1), which is 2.5 times of NiO electrodes. Moreover, the NiO/CA nanofibers show excellent cyclic performance after 1000 cycles.Graphical abstractThe possible formation process of NiO nanofibers without citric acid (a), and modified by citric acid (b). When the nanofibers is modified by citric acid, the nickel citrate is produced by complexing action of citric acid and nickel nitrate. Because of the larger space steric hindrance, the structure is limited by the molecular geometry. Under high temperature, the hollow nanofibers composed of NiO slices formed after the removal of PVP.Highlights► The method of obtaining hollow nanofibers is raised for the first time. ► The prepared NiO nanofibers are hollow tube and comprised of many NiO sheets. ► The hollow structure facilitated the electrolyte penetration. ► The hollow NiO nanofibers have good electrochemical properties.

Novel fluorescent Eu-containing layered double hydroxides (Eu-LDHs) were prepared by direct ion-exchange of EuMgAl-NO3 LDHs precursors with MoO42−MoO42− anions. The samples were characterized by elemental analyses, powder X-ray diffraction (XRD), Fourier transform infrared (FT–IR), Raman spectra, photoluminescence spectroscopy. The results indicated that Eu3+ ions were likely incorporated into the hydrotalcite lattice and MoO42−MoO42− anions were successfully intercalated into interlayer region of the LDHs with the Mo/Al molar ratio close to 0.40. The luminescence properties were largely enhanced compared with the EuMgAl-NO3 LDHs precursors, which were attributed to the energy transfer between Eu3+ and MoO42−MoO42−.Highlights► Novel fluorescent Eu-containing layered double hydroxides were prepared. ► Eu3+ ions were incorporated into the hydrotalcite lattice. ► MoO42− anions were successfully intercalated into interlayer region of the LDHs. ► The luminescence properties were largely enhanced compared with precursors. ► Such behaviors can be attributed to energy transfer from MoO42− to Eu3+ centers.

In this paper, we describe a general process for the synthesis of highly crystalline Zn–Ni–Al hydrotalcite-like materials. The structure and thermal decomposition of the prepared samples are studied by XRD, FT–IR, TG–DSC, SEM, TEM and N2 adsorption/desorption. The morphology of large-sized, porous and hexagonal platelike Zn–Ni–Al hydrotalcite is affected by calcination temperature. BET specific surface area and pore volume are observed to increase with increase of the calcination temperature up to 700°C followed by a further decrease with increasing temperature.

In order to enrich the variety of copper sulfide and enhance its currently existing applications, CuS nestlike hollow spheres assembled by microflakes were successfully synthesized through an oil−water interface route employing copper chloride, carbon disulfide, and sulfur as the starting materials in the presence of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. The composition, morphology, and structure of the product were characterized by X-ray powder diffraction, energy dispersive spectrometer, scanning electron microscopy, and transmission electron microscopy. The optical properties of the copper sulfide microstructures were investigated by UV−visible absorption spectra. Nestlike CuS microstructures were also explored as an additive to promote the thermal decomposition of ammonium perchlorate, and a thermogravimetric analysis technique was applied to investigate its catalytic performance. The results demonstrate that the product possesses good optical quality and catalytic performance, which indicate its broad potential applications. Because of its special hollow geometrical shapes and high surface areas, it can be used as catalysts, in sensors, as photonic crystals, and in light fillers. The current chemical strategy is expected to synthesize other metal sulfides or hollow structures.

The goal of this study is to prepare hydrotalcite pellets and validate their potential utility in catalysts and catalysts support. Hydrotalcite pellets were synthesized by urea hydrolysis. Urea hydrolysis can provide both carbonate as the intercalated anion and hydroxyl anions to form Mg–Al layered double hydroxide (LDH) with carbonate intercalation. Urea hydrolysis was also used to generate NH3 which plays a critical role in the process of synthesis hydrotalcite pellets. Mechanism of the formation hydrotalcite pellets was also discussed. The as-prepared samples were well characterized by X-ray diffraction, scanning electron microscopy, transmission electronic microscope, N2 adsorption/desorption, and Fourier transform infrared spectroscopy, respectively. The results revealed that the hydrotalcite pellets were well-crystallized and formed by self-assembly of hexagonal platelets LDHs. The present work suggests that it is possible to grow hydrotalcite pellets directly through one-step aqueous solution-phase chemical route under controlled conditions.

CuO shuttle-like and flower-like nanocrystals were synthesized through a one-step, low-temperature solution-phase method in the presence of a cation surfactant, hexadecyl trimethyl ammonium bromide. These nanocrystals were studied as an additive for promoting the thermal decomposition of ammonium perchlorate (AP). With the addition of CuO shuttle-like and flower-like nanocrystals, the thermal decomposition temperature of AP decreased. The structure, particle size, and morphology of resulting CuO powders were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis technique was applied to investigate the thermal decomposition of mixtures of AP and as-prepared CuO nanocrystals.

Chrysalis-like morphologies of CuO have been synthesized in large-quantity via a simple chemical deposition method without the use of any complex instruments and reagents. CuO nanocrystals showed a different morphology at three different temperatures, 25, 60 and 100°C. The particle size, morphology and crystal structure of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectra. The catalytic effect of CuO nanoparticles on the decomposition of ammonium perchlorate (AP) was investigated by STA 409 PC thermal analyzer at a heating rate of 10°C min−1 from 35 to 500°C. Compared with the thermal decomposition of pure AP, the addition of CuO nanoparticles decreased the decomposition temperature of AP by about 85°C.

The nanocrystalline CuO powders were prepared by precipitation method using Cu(NO3)2 as copper raw material, water and ethanol as dispersants, and NaOH and ammonia solution as precipitates. The structure, particle size and morphology of resulting CuO powders were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanism of CuO formation was discussed.

Synthesis of flower-shaped ZnO nanostructures composed of ZnO nanosticks was achieved by the solution process using zinc acetate dihydrate, sodium hydroxide and polyethylene glycol-20000 (PEG-20000) at 180°C for 4 h. The diameter of individual nanosticks was about 100 nm. Detailed structure characterizations demonstrate that the synthesized products are wurtzite hexagonal phase, grown along the [001] direction. The infrared (IR) spectrum shows the standard peak of zinc oxide at 571 cm−1. Raman scattering exhibits a sharp and strong E2 mode at 441 cm−1 which further confirms the good crystal and wurtzite hexagonal phase of the grown nanostructures.

•Sandwich-like hefero-structured V2O5/CNTs complex was synthesized.•The V2O5/CNTs complex exhibited significantly enhanced capacitive performance.•The V2O5/CNTs complex achieved a high capacitance of 553.33 F g−1 at 5 mV s−1.Sandwich-like, hetero-structured vanadium pentoxide/carbon nanotubes are prepared by incorporating modified carbon nanotubes (CNTs) into layered V2O5 sheets via a simple hydrothermal method. The CNTs ensure fast and smooth electron transfer between V2O5 sheets, leading to higher electrochemical performance compared with V2O5 sheets and bulk V2O5. As a result, the specific capacitance of the V2O5/CNTs complex reaches a value of 553.33 F g−1. The composite also exhibits good cycling stability and maintains 83% of original capacitance over 1000 cycles at 10 mA cm−2.Sandwich-like structure hetero-structured Vanadium Pentoxide/carbon nanotubes complex is prepared via hydrothermal method and self-assembly process.

Some inorganic quasi-two-dimensional nanomaterials such as cobalt–nickel hydroxides are kinetically facile for a capacitive charge storage process. However, high performance capacitive charge storage needs a balance of the ionic and electronic transporting, and to build up an integrated architecture on substrates step by step and utilize the interface better is still a key challenge. As the interfacial assembly has conflicted with our goals for high-performance capacitive charge storage process, we identify theoretically and experimentally binary cooperative nanoscale interfacial materials to solve the problem. Co–Ni-hydroxide precursors were prepared by hybrid quasi-two-dimensional nanosheets and hetero-oriented nanocrystallines walls. Followed by dip-dry and annealing, NiCo2O4 could adhere to the nickel foams robustly with a solution-based surface treatment. Moreover, an unusual phenomenon in the electrochemical test inspired us to establish a bridge between ‘supercapacitor’ and ‘battery’. The bridged gap highlights a new design idea for high-performance energy storage.

3D interconnected NiCo2S4 nanosheets have been directly grown on nickel foams using a facile two-step solution-based method. The as-prepared electrodes with controllable mass loadings and microstructures show excellent electrochemical performance, indicating their potential application as supercapacitors. Electrochemical measurements exhibit that the NiCo2S4/nickel foam electrode has a competitive areal specific capacitance (10.82 F cm−2 at 10 mA cm−2), relatively high rate capability (40.3% capacitance retention at 80 mA cm−2) and good cycling stability (92% capacitance retention after 1500 cycles at 20 mA cm−2).