Fabrication Of Electrospun Carbon Nanofibers/Metal Oxides Composite Materials And Their Applications In Photocatalytic And Supercapacitor Research

Carbon nanofibers （CNFs） show high conductivity and thermal conductivity, goodmechanical properties， chemieal stabllity, easy surfac efunctionalized and so on. In thisdissertation, In this dissertation, the valuable explorations have been focused on the designand synthesis of composite material, which has attracted special attention due to its widepotential application in many fields, such as catalysis and catalyst support chemical sensors,chemical cells, lithium-ion batteries, adsorbing material etc. In this dissertation, we employ anovel strategy to fabricate functional CNFs/metallic oxide nanocomposites by combining theelectrospinning technique and the solvothermal method. And the practical applications of theas-prepared functional nanocomposites materials are also investigated. The main researches arelist as follow:1. One-dimensional ZnO-carbon nanofibers （CNFs） heteroarchitectures with highphotocatalytic activity have been successfully obtained by a simple combination ofelectrospinning technique and hydrothermal process. The as-obtained products werecharacterized by field-emission scanning electron microscopy （FE-SEM）, energy-dispersiveX-ray （EDX） spectroscopy, transmission electron microscopy （TEM）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy （XPS）, and IR spectrum. The results revealed thatthe secondary ZnO nanostructures were successfully grown on the primary CNFs substrateswithout aggregation. And, the coverage density of ZnO nanoparticles coating on the surfaceof the CNFs could be controlled by simply adjusting the mass ratio of zinc acetate to CNFs inthe precursor during the hydrothermal process for the fabrication of ZnO-CNFsheterostructures. The obtained ZnO-CNFs heteroarchitectures showed high photocatalyticproperty to degrade rhodamine B （RB） because of the formation of heteroarchitectures,whichmight improve the separation of photogenerated electrons and holes. Moreover, theZnO-CNFs heteroarchitectures could be easily recycled without the decrease in photocatalyticactivity due to their one-dimensional nanostructural property.2One-dimensional In₂O₃nanocubes/carbon nanofibers （CNFs） heterostructures have beensuccessfully obtained by a simple combination of electrospinning technique and solvothermalprocess for the first time. Photocatalytic tests displayed that the In₂O₃/CNFs heterostructurespossessed a much higher degradation rate of rhodamine B （RB） than the pure In₂O₃undervisible light. The enhanced photocatalytic activity could be attributed to the formation ofheterostructures, which might improve the separation of photogenerated electrons and holes. Moreover, the In₂O₃/CNF heterostructures could be easily recycled without the decrease ofthe photocatalytic activity due to their one-dimensional nanostructural property. Themorphology of the secondary In₂O₃nanostructures （nanocubes, nanoagglomerates ornanoparticles） could be controlled by adjusting the additives including CO（NH2）2and adefined amount of water. The general growth mechanisms for the In₂O₃nanostructures havealso been discussed.3Tin oxide （SnO₂）/carbon nanofibers （CNFs） heterostructures were fabricated by combiningthe versatility of the electrospinning technique and hydrothermal process. The results revealedthat the SnO₂nanostructures were successfully grown on the primary electrospun carbonnanofibers substrates. And, the coverage density of SnO₂nanoparticles coating on the surfaceof the CNFs could be controlled by simply adjusting the mass ratio of CNFs to SnCl₄.5H₂O inthe precursor during the hydrothermal process for the fabrication of SnO₂/CNFsheterostructures. The electrochemical performances of the SnO₂/CNFs heterostructures as theelectrode materials for supercapacitors were evaluated by cyclic voltammetry （CV） andgalvanostatic charge discharge measurement in1M H₂SO₄solution. At different scan rates,all the samples with different coverage densities of SnO₂showed excellent capacitancebehavior. And, the sample CS2（the mass ratio of CNFs to SnCl₄.5H₂O reached1:7） exhibiteda maximum specific capacitance of187F/g at a scan rate of20mV/s. Moreover, after1000cycles, the specific capacitance retention of this sample was over95%. The high capacitivebehavior could be ascribed to the low resistance of SnO₂/CNFs heterostructures and rapidtransport of the electrolyte ions from bulk solution to the surface of SnO₂.4. Highly dispersed Fe₃O₄nanosheets on one-dimensional （1D） carbon nanofibers （CNFs）were firstly fabricated by combining the versatility of the electrospinning technique andsolvent-thermal process. The electrochemical performances of the Fe₃O₄/CNFsnanocomposites as the electrode materials for supercapacitors were evaluated by cyclicvoltammetry （CV） and galvanostatic charge–discharge measurement in1M Na2SO3electrolyte. At different scan rates, the sample showed excellent capacitance behavior.Incomparison to the pure Fe₃O₄（83F/g）, the as-prepared Fe₃O₄/CNFs nanocompositeselectrode exhibited a higher specific capacitance （135F/g）. Meanwhile, the supercapacitordevices of the Fe₃O₄/CNFs nanocomposites exhibited excellent long cycle life along with91%specific capacitance retained after1000cycle tests. The high capacitive behavior couldbe ascribed to the high electrical conductivity and the one-dimensional properties of the CNFsin Fe₃O₄/CNFs nanocomposites, which could decrease the charge transfer resistance of theFe₃O₄. At the same time, the high specific surface area and high level exposure of the Fe₃O₄nanosheets on the surface of the CNFs increased the electrochemical utilization of Fe₃O₄. Finally, a possible mechanism for the formation of the Fe₃O₄nanosheets on the surface ofCNFs was suggested.