Fabrication, Characterization And Application Of Carbon Nanotube Composite Materials

Owing to the small size effect, high surface effect and quantum size effect, nano particles exhibit excellent characters in catalyst fields. Be used as catalyst, nano particles show many excellent qualities, such as roughness surface, high surface area, high surface energy, short diffusion channel in crystal and much more surface active sites. These excellent qualities made the nano particles exhibit promising application in catalyst field.The diameter of nano scale particles is very small. The percentage of surface atomic is very high subsequently. For this reason, the nano particles are very easy to be aggregated and the catalysis activity and selectivity decreased therefore. To avoid this problems, dispersing the nano catalyst particles on the surface of carrier may be a good method. The structure and character of the catalyst supports take an important role in improving catalyst activity and increasing the quantity of the catalyst to be used. In this thesis, our main aim is to improve the performance of the catalyst supports and to exploit new catalyst carrier. Carbon nanotube composites will be introduced as catalyst in our work. Our main research is focused in two aspects:i . Base on that carbon nanotube can be resolved in aniline in reflux process, using the same method as electro-polymerization of pure polyaniline, we have fabricated carbon nanotube/polyaniline composites and used it as the catalyst supports in methanol and formic acid electro-oxidation.ii. Owing to their hollow structure and high surface area of carbon nanotube, together with their outstanding electrical conductivity and mechanic intension, carbon nanotubes are very suitable to be used as catalyst supports. How to deposited noble nanoparticles on the surface of carbon nanotube is an attractive issue. Because that the surface of carbon nanotube is inert, to deposit nobel nanoparticles on the surface of carbon nanotube directly is very difficult. Chemical modification of the carbon nanotube is an effective method to resolve this problem. In this thesis, we have derived the surface of carbon nano tube with mercaptobenzene moieties and a singlelayer of organic moieties is covered over the surface of carbon nanotube. This method is an effective way to help noble nanoparticles to be deposited on the surface of carbon nanotube.The main research of this thesis is as following:1. Multi-walled carbon nanotubes have been dispersed in aniline in the reflux process. UV-vis adsorption spectroscopy studies show that a charge-transfer interaction has been occurred between carbon nanotube and aniline molecular. According to TGA results, 1.3wt% of multi-walled carbon nanotube can be resolved in aniline.2. Polyaniline/multi-walled carbon nanotube composites have been fabricated by using electro-polymerization technique based on that MWNTs can be well dissolved in aniline. SEM observation shows that the porous structure of Polyaniline has been significantly changed by introduction of multi-walled carbon nanotube. There is considerable quantity of fibers in the composite matrix. They entangled to form a web structure and made the composites exhibit higher porosity and better permeability.3. The polyaniline/multi-walled carbon nanotube composites have be fabricated by electro polymerization of aniline with MWNTs concentration of 0.325, 0.65, 0.975, 1.3 wt% dissolved in, and the conductivity of the composites attaches to 28.38,46.489,72.089 and 89.276 S/cm respectively, much higher than pure polyaniline. It indicates that incorporation of multi-walled carbon nanotube into polyaniline matrix can influence the electric properties of the polymer.Platinum nano particles have been deposited on the presynthesized multi-walled carbon nanotube/polyaniline composite films at constant potential. The obtained composite films can be used as catalyst supports for electro oxidation of methanol and formic acid. Cyclic voltammogram and Chronoamperogram results show that platinum particles deposited on multi-walled carbon nanotube/polyaniline composite films exhibit higher electrocatalytic activity towards methanol and formic acid electro oxidation than that deposited on pure polyaniline films. On the other hand, theincrease of electrical conductivity of multi-walled carbon nanotube/polyaniline composites can facilitate electrons shuttling through composite films between the substrate and dispersed platinum particles. It is helpful to increase the electrocatalytic activity of the Pt modified multi-walled carbon nanotube/polyaniline electrode.5. The multi-walled carbon nanotubes have been functionalized with mercaptobenzene moieties. FT-IR, EDS and XPS results show that mercaptobenzene moieties have been attached to the ^-conjugated body of MWNTs successfully.6. By using the self-assemble technique, we have developed a new and effective method to robustly self-assemble gold nanoparticles onto the surface of carbon nanotubes. Transmission electron microscope images give direct evidences for the success of the attachment of gold nanoparticles onto the surface of MWNTs by taking advantage of strong thiol-Au interaction. The average diameter of the Au nanoparticles is 8.86 nm. The obtained hybrid nanostructure materials can be used in catalytic, electronic, optical, and magnetic applications.Aryl nature of high degree of deloclization electrons in benzene ring of mercaptobenzene could facilitate electron tunneling and hence reduce the electrical resistance between gold nanoparticle and MWNTs. This factor is very important for the obtained hybrid nanostructure for their utilization in various potential applications.