Research On Matal Supported B-C-N Nanotubes Prepared By Electrospinning

Nanomaterials have attracted a great deal of attention due to their excellentproperties. Among them, the catalytic properties of nanomaterials have becomenew prevalent research fields. Because of their larger specific surface area, thestability of chemical property, well conductive heat and conduction performance,and have been into large-scale preparation, carbon nanotubes are not only used asthe new type of catalyst carrier, but also directly as certain reaction catalyst.Many studies have shown that, carbon nanotubes loaded with metal nanoparticles,or doped with elements of B and N, have better catalytic performance. This paperstudies on the influence of metal nanoparticles and B/N doping on the carbonnanotubes prepared by electrospinning, and successfully synthesizes the B-C-Ncomposite nanotube samples loaded with metal nanoparticle. And the propertiesas electrocatalysts are investigated.This dissertation reports the preparation of the B-C-N composite nanotubesby using coaxial electrospinning technique.The DMF solution of PAN and PVDFmixture and dimethyl silicone oil are used as the shell solution and kernelsolution,respectively.The as-spun composite fibers are treated by thepre-oxidation process, B2O3dipping, and nitriding processing, in order to getB-C-N nanotubes. Then the B-C-N nanotube samples are impregnated with metalinorganic salt saturated solutions to get the B-C-N nanotubes loaded withmetal(Fe, Co, Cu or Ni)nanoparticle catalysts. This dissertation makes a detailedcharacterization of the structure and composition of the samples by SEM/EDX,TEM, XPS, FTIR, XRD and Raman methods. Fe, Co, Cu and Ag nanoparticlescan be loaded on the B-C-N nanotubes, but different metals result in differentmorphology. For exemple, the B-C-N nanotubes loaded with Co and Ninanoparticles exhibit drape and embedded morphology, which would bring greateffect on the catalyst performance.The effects of electrospinning parameters, on the morphology and structureof the B-C-N composite nanotubes are also discussed in this work. By controllingthe concentration of the polymer, we can control the diameter of the B-C-N nanotubes, in the range from0.5to1.0um.This work also studies the catalytic performance for the oxygen reductionreaction(ORR) of B-C-N composite nanotubes and the samples loaded withmetal(Fe, Co, Cu, or Ag)nanoparticles both in acid (0.5M H2SO4) and alkaline(0.1M KOH)solutions through comparing CV curves and RDE curves ofdifferent catalysts.The B-C-N nanotubes loaded with Ni nanoparticles showrelatively higher catalytic performance for ORR in alkaline medium.Finally, this dissertation analyzes the transferred electron numbers of thedifferent catalysts in different electrolytes, and then discusses the possiblereaction mechanism during ORR process. And feasible methods to furtherimprove electrocatalytic activity of this kind of materials for ORR are proposed.