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Silica- supported metal ball and Electrochemical Properties

Author: XieSiWen
Tutor: ChenShuang；XuChangWei
School: Wuyi University
Course: Applied Chemistry
Keywords: nanostructured materials core-shell structure Au/SiO2 alcohol oxidation glycerol
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 76
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Abstract


The core-shell structure composite nanomaterials are a kind of rising newfashioned composite materials. Because of the numerous merits on their’s own structure, the core-shell structure nanomaterials have already widely used in catalysis, sensor, multifunctional nanocomposite materials, insulate materials, biologic medicine and so on. In this thesis, the preparation of two type core-shell structure nanomaterials was reported. Furthermore, their properties were discussed carefully.The preparation of silica microspheres was based on the well-known Stober method. Then the surface-functionalized of silica microspheres was functionalized by 3-aminopropyltrimethoxysilane(APS) and polyethyleneimine(PEI) which adsorb the gold nanoparticles at room temperature. The last, gold nanolayer-encapsulated silica composite nanoparticles and nickel nanolayer-encapsulated silica composite nanoparticles were respectively synthesized using Au-functionalized silica particles as templates, Au-surface seeding and chemical reduction method. The morphology and structure of the core-shell composites nanomaterials were characterized using transmission electron microscopy (TEM) and scanning electron microscopy(SEM). The contents of metals in core-shell nanomaterials were analyzed using energy dispense spectroscopy(EDS) and X-ray diffraction(XRD) and the electrochemical activity for alcohols oxidation on core-shell nanomaterials was explored using cyclic voltammetry.The result show that the monodispersed silica microspheres with 200 nm size and uniform size, could be obtained in 4.7 mL tetraethoxysilane(TEOS),16 mL distilled water, 50 mL absolute ethyl alcohol and 25% ammonia. Silica particles functionalized with PEI were more effective at adsorbing gold nanoparticles forming than that functionalized with APS. The Au/SiO2 core-shell nanomaterials of smooth and complete nanoshell were produced by 0.01 g Au-functionalized silica microspheres and 500 mL aged HAuCl4/K2CO3 solutions at least. The rough surface of Ni/SiO2 core-shell nanomaterials and the needlelike nickel nanoparticles was caused by increasing the used amount of hydrazine hydrate and faster the reduction of Ni2+.At first, the electrochemical activity for alcohols oxidation on Pt, Pd and Au electrodes was studied. Glycerol was found that has a very high electrochemical oxidation activity on Au electrode and higher than that on the Pd electrode. Then the electrochemical activity for methanol, ethanol, n-propanol, isopropanol, ethylene glycol and glycerol oxidation on Au supported by silica microspheres was investigated in 1mol/L KOH solutions for the first time, and glycerol shows a very high activity with a very low loading of Au.

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