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Controllable Synthesis of Carbon Nanotubes Supported Metall Nanocatalysts and the Study on Their Ele

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Tutor: YangLin;LiWuJu
School: Henan Normal
Course: Inorganic Chemistry
Keywords: Fuel cells,Palladium based catalysts,Platinum based catalysts,untreated MWCNTs,c
CLC: O643.36
Type: Master's thesis
Year:  2011
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Abstract:
Due to the superior properties, such as high efficient, security, and environmental-benign, direct fuel cells have received considerable attention. However, there also have some drawbacks which limit their practical applications, one of which is the high cost of nobel metal catalysts. Therefore, many efforts have been made to improve the utilize ratio of catalysts and maximize the utilization of the catalysts to reduce the cost. It is well known that the utilization of the electrocatalysts is strongly related to the supports. As for the supports, carbon nanotubes (CNTs) are considered to be an attractive supporting material, owing to the high electrical conductivity, large surface to volume ratio, good thermal and chemical stability. However, pristine CNTs are chemically inert, it is necessary to activate the graphitic surface of the nanotubes to anchor and deposit catalyst nanoparticles facilely. Conventionally, CNTs are functionalized by harsh oxidative processes. Nevertheless, the harsh oxidative processes will cause defects on the surface of CNTs, which would impair the mechanical properties and reduce the electrical conductivity and corrosion resistance. Thus, there exists a need to develop a facile and effective method that not only provides well-dispersed metal nanoparticles with controlled size, but also has little or no damage to the structure of CNTs. To address these issues, we developed some strategies of using additions to functionalize the MWCNTs to anchor metal nanoparticles.In this paper, high performance Pt and Pd based catalysts were prepared via a variety of methods under milds conditions. The catalyst was characterized by High resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) patterns, measurements, Field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) spectra, Thermogravimetric analysis (TGA), Raman spectroscopy, and UV¨Cvis absorption spectra. The electrocatalytic properties, incluing the activity and stability, were analysised by cyclic voltammetry and chronoamperometry tests. The approximate experimental content was listed as follows:(1) We present an overview of the fuel cell, and give the conventional methods of fuel cell catalysts and the general research progress.(2) We reported on the preparation and characterization of Pd nanoparticles supported on untreated MWCNTs, which was synthesized in the presence of glutamate. Cyclic voltammetry and chronoamperometry tests demonstrated that the obtained Pd/MWCNT catalyst displayed superior electrocatalytic activity and stability in formic acid oxidation.(3) A facile and effective method was used to prepare Pt nanoparticles dispersed on the surface of pristine multi-wall carbon nanotubes (P-MWCNTs), using sodium phthalate (SP) as a special additive, and ethylene glycol (EG) aqueous solution as an effect solvent. The as-prepared Pt nanoparticles (2.2nm) was highly dispersed with a narrow size distribution, which exhibited higher electrocatalytic activity for methanol oxidation. Additionally, we developed a new strategy to prepare Pt-SnO_x nanoparticles on 8-Hydroxyquinoline (HQ) functionalized MWCNTs. The obtained catalyst possesses a good capacity for preventing CO poisoning and displays better electrocatalytic activity and stability for the methanol oxidation.(4) The influence of tri-metal catalyst on the improvement of catalysts for methanol oxidation was intensively studied. Firstly, a high performance nanocatalyst with heterostructure (Pt decorating PdCo nanopaticles supported on untreated MWCNTs) foris successfully prepared via a solvothermal method. Then, Pt particles with diameters about 1.8nm were formed on the surface of PtCo alloy compound. Compared with simple catalysts, the tri-metal catalyst has higher electrocatalytic activity and better stability, which could be attributed to the synergistic effect between Pt and PdCo resulting in the higher utilization of Pt in the Pt-PdCo/MWCNTs catalyst.The above results not only provide new methods for the supporting matel nanoparticles on the untreaded MWCNTs, but also give the new try to improve the utilization of the nobel metal and solve the problem of CO poisoning.
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