Preparation And Properties Of Nanoparticles/C Composites By Molten Salt Method

Monodisperse nanomaterials exhibit special physical and chemical properties because of their uniform size distribution, controllable surface property and quantum size effect which lead to the broad application prospects in nano-catalysis, the high density information storage, building functional nanomaterials, biological fluorescence labeling and magnetic resonance imaging. Currently, there are a series of methods to prepare the monodisperse nanomaterials using the long carbon chain organic molecules such as oleic acid and oil amine as surfactant. However, when these monodisperse nanoparticles are used in catalysts, gas sensors, electrochemical and other fields, the long carbon chains of organic molecules wrapped on the surface of the nanoparticlesbecome the obstacles. Therefore, how to obtain monodisperse nanomaterials and remove the organic molecules coated by the synthesis process, and the application field of the catalytic, gas sensing and electrochemistry, is of great significance. In this paper, Bi-Bi2O3/C, CoO/C and Ni/C nanocomposites were prepared via molten salt method by adjusting the experimental parameters. Finally, the properties of the as-obtained nanomaterials, including photocatalytic, electrochemistry and gas sensing have been studied. The details are as follows:Bi-based nanomaterials: carbon-encapsulated Bi-Bi2O3 nanospheres were prepared by decomposing Bi(OH)3@OA complex through a salt-template process. The obtained samples were analyzed by X-ray diffraction(XRD), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The TEM and SEM images showed that the Bi-Bi2O3 nanospheres with a lateral size of 20-60 nm. The XRD result showed that the products were rhombohedral Bi and tetragonal Bi2O3. The photocatalytic properties of the Bi-Bi2O3/C nanocomposites were studied. The sample prepared at 400 oC exhibited a higher degradation activity for both methylene blue(MB), methyl orange(MO) and Rhodamine B(RhB).Co-based nanomaterials: carbon-encapsulated CoO nanoparticles were prepared by decomposing Co(OH)2@OA complex through a salt-template process and their applications as the lithium-ion battery anodes. The TEM and SEM images showed that the CoO nanoparticles prepared at different temperatures with the diameter among 7-12 nm. Through the XRD patterns of CoO, the samples are matched well with the standard card with the cubic phase of CoO. The electrochemical properties shows that the initial discharge capacities for the sample prepared at 400 oC is 1139.1 mAh·g-1, the reversible capacity is 642.1 mAh·g-1 after 50 discharge/ charge cycles and the capacity retention rate is 95%.Ni-based nanomaterials: carbon-encapsulated Ni nanoparticles were prepared by decomposing Ni(OH)2@OA complex through a salt-template process. By controlling the temperature, when the calcination temperature is 400 oC, the size and morphology of the uniform Ni/C nanomaterials are obtained. The hollow structure Ni O spheres of 20-70 nm can be obtained by using Kirkendall effect with different temperature and time. Finally, the gas sensing properties of NiO hollow spheres were measured by detection of methanol, ethanol, cyclohexane, benzene, ethyl acetate and acetone at 200-400 oC. The NiO-4 show the excellent selectivity and gas response to n-butanol(1000 ppm, Rg/Ra=9.0 at 240oC).