Controllable synthesis of nickel hydroxide and porous nickel oxide nanostructures with different morphologies

Alpha-Ni(OH)(2) nanobelts, nanowires, short nanowires, and beta-Ni(OH)(2) nanoplates have been successfully prepared in high yields and purities by a convenient hydrothermal method under mild conditions from very simple systems composed only of NaOH, NiSO(4), and water. It has been found that the ratio of NaOH to NiSO(4) not only affects the morphology of the Ni(OH)(2) nanostructures, but also determines whether the product is of the alpha- or beta-crystal phase. A notable finding is that porous NiO nanobelts were produced after exposure of the Ni(OH)(2) products to an electron beam for several minutes during transmission electron microscopy (TEM) observations. Another unusual feature is that rectangular nanoplates with many gaps were obtained. Furthermore, porous NiO nanobelts, nanowires, and nanoplates could also be obtained by annealing the as-prepared Ni(OH)(2) products. A sequence of dissolution, recrystallization, and oriented attachment-assisted self-assembly of nanowires into nanobelts is proposed as a plausible mechanistic interpretation for the formation of the observed structures. The method presented here possesses several advantages, including high yields, high purities, low cost, and environmental benignity. It might feasibly be scaled-up for industrial mass production.     

利用均相沉淀剂和形貌导向剂水热一步合成层状镍钴氢氧化物

本文利用在反应过程中同时添加均相沉淀剂六次甲基四胺和形貌导向剂十六烷基三甲基溴化铵,结合水热反应的方法一步合成了镍钴氢氧化物. 随着六次甲基四胺的水解,层状镍钴氢氧化物可以被合成而且避免了额外碱源的使用;同时,由于反应过程中十六烷基三甲基溴化铵参与的孔径调节,合成出来的镍钴氢氧化物具有可控的介孔尺寸13.4 nm以及较大的比表面积93.6 m²•g^-1. X射线衍射图谱表明合成出来的镍钴氢氧化物构型是α-Ni(OH)₂-β-Co(OH)₂. 扫描电镜表明合成出来的镍钴氢氧化物具有层状的结构. 正是因为层状介孔结构的存在,合成出来的镍钴氢氧化物在1A•g^-1电流密度下,比电容可以高达1902 F•g^-1;即使电流密度提高到8 A•g^-1,镍钴氢氧化物的比电容仍然可以保持在1250F•g^-1.     

Hydrothermal synthesis of precursors of neodymium oxide nanoparticles

The nanometric precursors of neodymium oxide of various morphologies were prepared via a hydrothermal reaction route. The precursors and their thermal evolution to neodymium oxide phase were characterised by means of X-ray diffraction (XRD), transmission electron microscopy (TEM, HRTEM), thermal analysis (TG, DTA, EGA-MS), FTIR and atomic force microscopy (AFM). It was found that the reaction conditions (temperature, pressure) played a key role for the product formation of desired morphology and structure. At mild conditions (140 °C) precursor with unusual fibrous morphology and Nd(OH)_2.45(Ac)_0.550.45H₂O stoichiometry was obtained. Upon heating this phase transformed, via intermediate cubic oxide, into trigonal Nd₂O₃ at 800 °C. Nd(OH)₃ hydroxide obtained at severe conditions (180 °C) transformed upon heating into cubic Nd₂O₃ phase at about 500 °C and this phase was stabilised even at 800 °C. The fibrous precursors appeared to be a convenient material for preparation of homogeneous thin coatings on planar substrates is shown.     

氢氧化镍纳米棒的水热制备及其表征

以Ni₂SO₄·6H₂O和NaOH为原料,在水热条件下制备了氢氧化镍纳米棒.运用透射电子显微镜(TEM)和X射线衍射仪(XRD)对样品进行了表征,考察了水热反应温度和pH值对产物的形貌和结构的影响.结果表明,氢氧化镍纳米棒形成的最佳条件是180～200℃,pH为9～10.     

Exfoliated nickel hydroxide nanosheets for urea electrolysis

Two-dimensional nickel hydroxide nanosheets were synthesized by exfoliating surfactant intercalated layered nickel hydroxides and developed as electrocatalysts for urea electro-oxidation. The electro-oxidation of urea on Ni(OH)₂ nanosheet modified electrodes shows a decrease of 100 mV in overpotential and an enhancement in current density, which reaches ca.154 mA cm^{− 2} mg^{− 1}, by a factor of ca. 170 compared to bulk Ni(OH)₂ powder modified electrodes. The Ni(OH)₂ nanosheets have promising applications in urea-rich wastewater remediation, hydrogen production, electrochemical sensors, and fuel cells due to their ability to promote the urea electrolysis reaction.     

酒石酸掩蔽铝-丁二酮肟重量法测定镍钴铝三元氢氧化物中镍

镍钴铝三元氢氧化物中Ni质量分数为45%~60%、Al为0.5%~1.5%,丁二酮肟沉淀镍的pH条件下,Al3+会水解沉淀而干扰测定。试验对丁二酮肟重量法进行改进,采用酒石酸作为Al的掩蔽剂,从而建立了酒石酸掩蔽铝-丁二酮肟重量法测定镍钴铝三元氢氧化物中Ni含量的方法。试验评价了Al对丁二酮肟重量法测Ni的干扰,并确定了酒石酸的最佳掩蔽用量,测定实际样品801505型镍钴锰三元氢氧化物（Ni0.8Co0.15Al0.05(OH)2）和851005型镍钴锰三元氢氧化物（Ni0.85Co0.1Al0.05(OH)2）的RSD（n=11）分别为0.24%、0.31%,加标回收率分别为100.20%、99.68%,且测定值与ICP-AES基本一致。     

Mathematical models of the nickel hydroxide active material

A review is presented of the mathematical models that have been developed to describe the phenomena that occur in the active material in the nickel electrode. The review includes models that describe the reaction thermodynamics, proton diffusion, electron conductivity, semiconductor effects, and the reactions in the solid phase. The appropriateness of these models and their usefulness in predicting phenomena observed in nickel-based batteries are discussed. Received: 17 October 1999 / Accepted: 26 December 1999     

Room temperature solution-phase synthesis of flower-like nanostructures of [Ni3(BTC)2·12H2O] and their conversion to porous NiO

Hierarchical flower-like architectures of[Ni₃（BTC）₂·12H₂O]（BTC³=benzene-1,3,5-tricarboxylate） were successfully prepared by a simple solution-phase method under mild conditions without any template or surfactant.Phase-pure porous NiO nanocrystals were obtained by annealing the Ni-BTC complex without significant alteration in morphology.The product was characterized by X-ray diffraction techniques,field-emission scanning electron microscopy（FESEM）.transmission electron microscopy（TEM） and high-resolution TEM（HRTEM）.The catalytic effect of the NiO product was investigated on the thermal decomposition of ammonium perchlorate（AP） and it was found that the annealed NiO product has higher catalytic activity than the commercial NiO.     

Hydrothermal assembly and structural characterization of an unprecedented one-dimensional chain constructed from nickel diphosphopentamolybdate clusters

A novel molybdenum phosphate complex, [Ni(1)(en)₂(PO₄)₂Mo₅O₁₅][Ni(2)(en)₂- (H₂O)₂]?·?H₂en?·?3H₂O (1), has been synthesized under hydrothermal conditions. The complex was characterized by elemental analysis, FT-IR, DTA/TG and single crystal X-ray diffraction. The compound is orthorhombic, space group P2₁2₁2₁, with a?=?12.580(3), b?=?17.676(4), c?=?17.969(4)?Å, V?=?3995.5(15)?ų, Z?=?4, and was refined to R ₁?=?0.0301, wR ₂?=?0.0715. It possesses an unprecedented one-dimensional chain structure constructed from molybdenum phosphate clusters and nickel complex fragments.     

Controlled synthesis of CuO nanostructures by a simple solution route

A simple solution route has been developed to prepare nanostructured CuO with Cu(NO₃)₂·3H₂O and NaOH as starting materials. CuO nanoribbons or nanorods and their assemblies into hierarchical structures have been synthesized, respectively, by controlling the molar ratio of NaOH to Cu(NO₃)₂, reaction temperature and the concentration of the starting NaOH solution. Experiments demonstrate that the molar ratio of NaOH to Cu(NO₃)₂ is an important parameter which may decide whether CuO exists in nanoribbons (nanorods) or assemblies into hierarchical structures. Whether Cu(NO₃)₂ is dissolved in ethanol or water also influences the formation of monodispersed CuO nanoribbons (nanorods). The growth mechanism of these nanostructures is discussed. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy (HRTEM) and their optical absorption spectra were also studied.     

Controllable synthesis of zinc-substituted alpha- and beta-nickel hydroxide nanostructures and their collective intrinsic properties

A new controllable homogeneous precipitation approach has been developed to synthesize zinc-substituted nickel hydroxide nanostructures with different Zn contents from a zinc nanostructured reactant. As typical layered double hydroxides (LDHs), zinc-substituted nickel hydroxide nanostructures can be formulated as NiZnx(Cl)y(OH)2(1+x)-y.z H2O (x=0.34-0.89, y=0-0.24, z=0-1.36). The structure and morphology of zinc-substituted nickel hydroxide nanostructures can be systematically controlled by adjustment of the zinc content. The effects of temperature and the amounts of ammonia and zinc nanostructured precursor on the reaction were systematically investigated. In our new method, although zinc-substituted alpha-and beta-nickel hydroxides have the typical 3D flowerlike architecture and stacks-of-pancakes nanostructures, respectively, their growth processes are different from those previously reported. A coordinative homogeneous precipitation mechanism is proposed to explain the formation process of zinc-substituted nickel hydroxide nanostructures. The zinc-substituted nickel hydroxide nanostructures exhibit some interesting intrinsic properties, and changing the zinc content can effectively tune their optical, magnetic, and electrical properties.     

Surfactant effects on pH-controlled synthesis of nickel hydroxides

The aim of the present work is to determine at 60 °C, the influence of the specific nature of nickel salt and pH on nickel hydroxide features such as crystallographic structure and morphology. Within the range 8 ≤ pH ≤ 11.5, a home-made nickel functionalized surfactant, nickel di-dodecylsulfate Ni(C₁₂H₂₅SO₄)₂ is compared to usual salts (nickel nitrate Ni(NO₃)₂ and nickel sulfate NiSO₄). In both cases, a sharp transition appears for pH about 10. In the classic salt case, the transition mainly affects morphology, that could be evidenced by the crosschecking of complementary techniques as SEM and nitrogen gas adsorption. For pH < 10, β-Ni(OH)₂ platelets are yielded, whereas more basic conditions lead to randomly aggregated nano-grains of badly crystallized β hydroxide. Inversely, by employing the functionalized surfactant, 2D morphology is maintained in the whole pH-range, but the crystal structure is pH-controlled ( phase with interlamellar dodecylsulfate for pH ≤ 9.5, and β phase for pH ≥ 10.5).     

Microwave assisted synthesis of manganese mixed oxide nanostructures using plastic templates

The synthesis method for obtaining sub-micrometric structures of rare earth manganese-based mixed oxide compounds is described. Pore wetting of porous polycarbonate templates with the liquid precursor was followed by a two-stage thermal treatment to obtain single phase La_0.325Pr_0.300Ca_0.375MnO₃ hollow and solid structures, with external diameter determined by the sacrificial template pore size. The first thermal stage, a microwave assisted denitration process, determines the shape of the structures. The second treatment, performed at 1073 K, allows to obtain the crystallographic structure of the compound. A variety of techniques (scanning and transmission electron microscopy, scanning probe microscopy) allowed to fully characterize the microstructure and morphology of these self-standing manganite nanostructures. For 1 μm pore size templates we obtained tubes, with external diameter around 800 nm and wall thickness around 150 nm; densely packed nanoparticles sized 20-50 nm are the building blocks of the walls. For pore size below 0.1 μm, solid nanowires were obtained, the size of constituent crystallites being around 10 nm. Overall obtained material exhibits ferromagnetic ordering below 200 K.     

Hydrothermal synthesis,crystal structure and antibacterial studies of nickel(II) and manganese(II) complexes with ciprofloxacin

Hydrothermal treatments of ciprofloxacin with Ni(NO₃)₂·6H₂O and Mn(ClO₄)₂·6H₂O yield two metal complexes: [Ni(H-cip)₂(H₂O)₂](NO₃)₂·2H₂O (1) and [Mn(H-cip)₂(H₂O)₂] (ClO₄)₂·2H₂O (2), confirmed by elemental analysis, IR and single crystal X-ray diffraction analyses. Complexes 1 and 2 were screened for antibacterial activity against Staphylococcus aureas, E. coli, Pseudomonas aeruginos and Candidaalbicans.     

A nonstoichiometric structural model to characterize changes in the nickel hydroxide electrode during cycling

Experimental capacities and mass changes are recorded using an electrochemical quartz crystal microbalance during the first nine charge and discharge cycles of nickel hydroxide thin films cycled in 3.0 weight percent (wt%) potassium hydroxide electrolyte. For the first time, the film capacities have been corrected for the oxygen evolution side reaction, and the data used as input into a point defect-containing structural model to track the changes that occur during short-term cycling. Variations in capacity and mass during formation and charge/discharge cycling are related to changes in the point defect parameters, thus providing a structural origin for the unique experimental variations observed here and often reported in the literature, but previously unexplained. Proton-, potassium-, and water-content vary in the active material during charge/discharge cycling. The observed capacity loss, or capacity fade, is explained by incomplete incorporation of potassium ions in (or near) the nickel vacancy during charge, as additional protons are then allowed to occupy the vacant lattice site. The increase in water content during reduction parallels the expansion of the electrode that is well known during cycling. This result confirms the origin of the swelling phenomenon as being caused by water incorporation. The model and methodology developed in this paper can be used to correlate electrochemical signatures with material chemical structure.

Surfactant-free synthesis of nickel nanoparticles in near-critical water

Nickel nanoparticles have been produced by combining two well-tested methods: (i) the continuous flow supercritical reactor and (ii) the reduction of a nickel salt with hydrazine. The normal precipitation of a nickel-hydrazine complex, which would complicate pumping and mixing of the precursor, was controlled by the addition of ammonia to the precursor solution, and production of nickel nanoparticles with average sizes from 40 to 60 nm were demonstrated. The method therefore provides some size control and enables the production of nickel nanoparticles without the use of surfactants. The pure nickel nanoparticles can be easily isolated using a magnet.     

Preparation of nickel oxide and carbon nanosheet array and its application in glucose sensing

Nickel oxide and carbon (NiO/C) nanosheet array was fabricated on Ti foil for the first time by calcining the precursor, which was synthesized through the hydrothermal reaction of nickel acetate, urea and glucose. The slow release of OH⁻ by the hydrolysis of urea aided in the direct nucleation and adhesion of precursor seeds on Ti substrate. The presence of carbon ensured a large specific surface area and good conductivity of the final NiO/C composite. The prepared NiO/C nanosheet array exhibited higher catalytic oxidation activity of glucose compared with the pure NiO nanosheet at a detection limit of 2 μM, linear range up to 2.6 mM (R²=0.99961), and sensitivity of 582.6 μAm M⁻¹ cm⁻². With good analytical performance, simple preparation and low cost, this composite is promising for nonenzymatic glucose sensing.     

高性能球型氢氧化亚镍的ICP-OES分析方法

建立了镍氢电池正极材料氢氧化亚镍中主成分锌、钴及杂质钙、镁、锰、镉的ICP AES测定方法。选择了仪器最佳工作条件 ,研究了镍基体对被测元素的干扰。方法的回收率为 95 .9%～ 1 0 3% ,RSD为 0 .93%～ 1 8%。     

Hydrothermal synthesis of NiS nanobelts and NiS2 microspheres constructed of cuboids architectures

NiS nanobelts of hexagonal phase have been hydrothermally synthesized starting from Ni(CH₃COO)₂·4H₂O and Na₂S₂O₃·5H₂O at 200 °C for 12 h. The as-prepared nanobelts were 50 nm thick, 70-200 nm wide and more than 10 μm long. As ethylenediaminetetraacetic acid (EDTA) added, in similar condition, 2 μm NiS₂ microspheres of cubic phase were prepared. However, as Ni²⁺/ ratio was 1:1 and the temperature was decreased to 160 °C, 5 μm NiS₂ microspheres constructed of cuboids were formed.     

Hydrothermal synthesis of single-crystal CeCO3OH and their thermal conversion to CeO2

Hexagonal single-crystalline cerium carbonate hydroxide （CeCO3OH） precursors with dendrite morphologies have been synthesized by a facile hydrothermal method at 180 C using CeCl3-7H2O as the cerium source, triethylenetetramine as both an alkaline and carbon source, with triethylenete- tramine also playing an important role in the formation of the dendrite structure. Polycrystalline ceria （CeO2） have been obtained by calcining the precursor at 500 C for 4 h. Tile morphology of the precursor was partly maintained during the heating process. The optical absorption spectra indicate the CeO2 nano/microstructures have a direct band gap of 2.92 eV, which is lower than values of the bulk powder due to the quantum size effect. The high absorption in the UV region for CeO2 nano/microstructure indicated that this material was expected to be used as UV-blocking materials.