| Carbon nanotubes and carbon fibers as the most important parts of carbon materials, they not only inherit excellent physical and chemical properties from the nanomaterials, but also have superior electronic conductivity, high resistance to corrosion and high stability origined form unique structure of the graphite layer. They are broadly applied as sensors, semiconductors, catalysts and catalyst supports, energy storage materials, super capacitors, biomedicine and other fields. At prsent, it is scientific valuable and has important practical significance to develop a facile, green, efficient and controllable method to prepare this class of materials. The carbon materias can be synthesized by controlling the experimental parameters, such as used catalysts, carbon sources, reaction temperatures, gas flow rates and feedstock pressures. Among them, the type and character of utilized catalyst is the most important factor in the formation of helical nanostructures. The catalysts act as the seeds for the nucleation and growth of nanotubes. Therefore, many researchers actively explore facile preparation methods of multi-morphology carbon materials and catalysts and investigate the effect on the structure and composition of carbon materials, in order to obtain carbon materials with high-quality and superior performance.Layered double hydroxides (LDHs), also known as anionic clay with brucite (Mg(OH)2)-like structure, consist of positively charged layers and negative anions in the interlayer. The metal ions are bonded to hydroxyl groups to form two-dimensional brucite-like layers and are uniformly distributed on an atomic level without segregation. Thus, highly dispersed metal particles over oxides matrix can be obtained by designing an appropriate LDHs precursor containing the desired metal cations and subsequent thermal treatment followed by reduction, originating from the ordered prearrangement of metal cations in the layers of LDHs precursor at an atomic level.In this thesis, utilizing good dispersion of cation within the LDHs'layered, multi-walled carbon nanotubes with uniform outer diameters has been grown over a series of catalysts derived from calcined LDHs by the CCVD method. The investigation of reaction temperature and compositions of LDHs in order to research the effect on the compositions of LDO and the growth of CNTs. To prepare metal-supported catalysts from calcined LDHs for the growth of CNTs not only overcome the shortcomings of active metal particles easily sinter during the reaction, but also control varying compositions of LDHs with different proportions to control the morphologies of CNTs. This method is simple, controllable, and environmentally friendly.Carbon nanotubes have been prepared by one-step synthesis over LDHs. In the system, LDHs is used directly as catalysts and acetylene act both as reducing agent and carbon source. Multi-walled CNTs were synthesized catalytically by active Ni nanoparticles derived from LDHs, and that the co-growing spinel-type NixMg1-xAl2O4 complex metal oxides from LDHs could be highly dispersed in the CNTs matrix. The as-synthesized spinel particles have good crystallinity and uniform particle size result in strong interaction between complex metal oxides and CNTs. This method is simple, effective and controllable. Moreover, the defect and the special surface modification by complex metal oxides on CNTs in favor of better performance of CNTs.Carbon fibers with different morphologies were prepared via CCVD of acetylene over LDHs. Carbon fibers including submicrometer fibers(SSCFs), helical carbon fibers (twist-shaped nanocoils CNCs and herringbone-type double microcoils CMCs) and lace-type carbon fiber (LCFs) could be controllably obtained only by varying compositions of LDHs.Finally, the electrocatalytic activity of electrodes modified with platinum particles supported on as-synthesized a series of carbon materials were studied for the oxidation of methanol/ethanol, as to demonstrate the feasibility of applying carbon materials as Pt electrocatalyst supports in direct alcohol fuel cells. The electrochemical investigation indicates that all as-fabricated electrodes showed superior electrocatalytic properties. The significantly enhanced electrochemical properties were believed to be strongly related to the special microstructure as well as the composition of as-grown carbon-based support materials. Moreover, the method of highly dispersed Pt nanoparticles supported on carbon nanotubes synthesized by a facile and green carbothermal reduction has been proposed. The as-fabricated hybrid Pt-CNTs composite exhibited excellent electrocatalytic property for ethanol oxidation.
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