| Because of unique crystal structure and special properties, cobalt-nickel based nanomaterials are widely used in super capacitors, cell, sensor, optics, catalysis, magnetic, and other fields, which have drawn enormous interests of researchers. In this dissertation, on the basis of chemical precipitation method at room temperature, polyvinyl pyrrolidone （PVP） was chosen as stabilizing agent and surface active agent, and graphene-like cobalt-nickel double hydroxide nanocomposites α-Co（OH）2/α-Ni（OH）2 have been successfully prepared. The catalytic and adsorption properties of as-prepared nanocomposites were investigated firstly. Then, Co3O4/NiO nanocomposites were obtained via calcining α-Co（OH）2/α-Ni（OH）2 nanocomposites at 350℃ in N2 atmosphere. Finally, Co3O4/NiO nanocomposites and α-Co（OH）2/α-Ni（OH）2 nanocomposites were made into single electrodes, and their electrochemical tests were conducted in a three-electrode system. In addition, the other Co3O4/NiO nanocomposites and single components were synthesized by a two-step method, which contained chemical precipitation and calcinations, and their electrochemical properties were also investigated. Main research contents are as follow:1. Synthesis of graphene-like a-Co（OH）2/a-Ni（OH）2 nanocomposites and their catalytic and adsorption propertiesCo（NO3）2·6H2O and NiCl2·6H2O were chosen as cobalt and nickel sources, respectively, PVP as stabilizing agent and surface active agent, and an alkaline condition being provided by hydrolysis of NaBH4 in aqueous solution. Graphene-like cobalt-nickel double hydroxide nanocomposites were successfully prepared at the room temperature. The samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, thermal gravimetric analysis （TGA） and physical property measurement system （PPMS）. Some parameters, such as reaction temperature, the type and amount of stabilizing agents, affect the structure and morphology of the as-prepared samples. The specific surface area of the sample reaches 260.1 m2/g. The nanocomposites were used as catalysts for the hydrogenation of p-nitrophenol and as adsorbents for the adsorption of methyl blue. The result showed that as-synthesized nanocomposites α-Co（OH）2/α-Ni（OH）2 have exhibited more efficient catalytic activity than single components for the hydrogenation of p-nitrophenol. In addition, the nanocomposites displayed prominent adsorption property for organic dyes methyl blue.2. Electrochemical properties of fim-like cobalt-nickel double oxide nanocomposites Co3O4/NiO.According to the TG curve, a kind of cobalt-nickel double oxide nanocomposites was obtained by calcining α-Co（OH）2/α-Ni（OH）2 in nitrogen atmosphere at 350℃. XRD, SEM, TEM techniques were used to characterize the structure, morphology of as-prepared samples. The as-obtained Co3O4/NiO also has graphene-like films with wrinkle structure. Then electrochemical properties tests of Co3O4/NiO and α-Co（OH）2/α-Ni（OH）2 were investigated in a three-electrode system by cyclic voltammetry and chronopotentiometry, with 6 M KOH being used as electrolyte. The result indicated that the nanocomposites Co3O4/NiO had a higher specific capacitance than α-Co（OH）2/α-Ni（OH）2 at high current densities. As to capacitance stability, the specific capacitance of Co3O4/NiO changed a little when the current density increased. Therefore, the capacitance stability of as-prapared samples Co3O4/NiO was improved by calcinations, as well as their specific capacitance.3. Synthesis of porous Co3O4/NiO and their electrochemical capacitive behaviorAnother cobalt-nickel double oxide nanocomposite Co3O4/NiO was synthesized by a two-step method. COCl2·6H2O and NiCl2·6H2O were chosen as the cobalt and nickel sources, respectively, K2C2O4·H2O as the precipitation agent, PVP as the structure-directing agent and stabilizing agent. Firstly, the precursors COC2O4/NiC2O4 were synthesized at room temperature by chemical precipitation. Secondly, according to the TG-DTG curves of the precursors in the oxygen atmosphere, the suitable temperature was chosen as calcined temperature. Co3O4/NiO nanocomposites were obtained at 500℃ in O2 atmosphere. The obtained samples were characterized by XRD, SEM, TEM, XPS, TGA and PPMS techniques. The results showed that some reaction parameters, including synthesis temperature, kinds and dosage of the surfactant active agent, affect the structure and morphology of the products. The as-synthesized samples were made into the working electrodes. The electrochemical properties of the working electrodes were tested in a three-electrode system, and 6 M KOH was used as electrolyte. Electrochemical capacitive behaviors of the synthesized products were investigated by electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and electrochemical impedance spectra. Interestingly, compared with single components, the obtained nanocomposites Co3O4/NiO exhibited enhanced specific capacitance. |
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