Fabrication Of One-Dimensional Composite Nanomaterials And Their Catalytic Properties Based On Electrospinning

In the past few years, one-dimensional (1D) nanostructures have attracted a lot of attention due to their novel properties including the high surface-to-volume ratio, high aspect ratio and intriguing applications in many areas such as nanoelectronic devices, biological and chemical sensors, battery and electrode materials, filter, environmental, biomedical and catalysis applications. A large number of advanced techniques have been developed to fabricate 1D nanostructures with well-controlled morphology and chemical composition. Among these methods, electrospinning seems to be the simplest and most versatile technique capable of generating 1D nanostructures from a variety of polymers. One of the most important advantages of the electrospinning technique is that it is relatively easy and not expensive to produce different kinds of nanofibers. Other advantages of the electrospinning technique are the ability to control the fiber diameters, the high surface-to-volume ratio, high aspect ratio, and pore size as non-woven fabrics. The advantage of the facile formation of 1D composite nanomaterials via electrospinning affords the materials multifunctional properties for various applications.In this thesis, the 1D composite nanofibers were prepared via electrospinning combined with sol-gel, gas-solid, carbonization and co-deposition. The 1D composite nanofibers were used as photocatalysis, electrocatalysis and chemicatalysis. The thesis was devided into three parts based on the three kinds of catalysis.Firstly, the trasition metal ions (tungsten ions) and rare earth ions (erbium ions) were doped into the titanium dioxides nanofibers based on the electrospinning technique combined with sol-gel. The composite nanofibers were characterized by SEM, TEM, XRD as well as N2 adsorption/desorption isotherm. The photocatalysis activity of the two kinds of composite nanofibers was investigated by employing the methylene blue as probe. A series of experiment were done to investigate the optimal experimental conditions including the doping content and calcination temperature. The UV-Vis analysis proved that ions doping can narrow the band gap of the titanium dioxides to absorb more visible light. The photodegradation mechanisms for the methylene blue were proposed based on our experiments.Secondly, two kinds of platinum nanoparticles-loaded on carbon nanofibers (CNFs) were synthesized by electrospinning and reduction (thermal in situ reduction and chemical reduction). These composite materials possess high electrochemically active surface area and good conductivity, and are ideal candidate for electrode materials. A high density of metal nanoparticles (catalytic sites) could be obtained by using the electrospinning technique. The interesting three-dimensional (3D) structure of platinum nanoparticles-loaded on CNFs may result in a large effective platinum surface area and good electrocatalytic properties. Through the SEM characterization, the platinum nanoparticles-loaded on CNFs films were 3D networklike structure and the porous structure could significantly increase the effective electrode surface and facilitate the diffusion of analytes into the films. This nanocomposite materials exhibited high electric conductivity and accelerated the electron transfer, as verified by the cyclic voltammetry. The platinum nanoparticles-loaded on CNFs-modified glassy carbon electrode domenstrated direct and mediatorless responses to H2O2. The analytical performances of the platinum nanoparticles-loaded on CNFs-modified glassy carbon electrode towards reduction of H2O2 were evaluated. The high sensitivity, wide linear range, good reproducibility and selectivity make the platinum nanoparticles-loaded on CNFs-modified glassy carbon electrode a promising candidate for amperometric H₂O₂.Thirdly, the novel Fe3O4-carrying composite PAN nanofibers were prepared via the electrospinning combined with co-deposition method and taken as an effective iron source for degradation of organic pollutants in Fenton-like system. In our present study, the Fe3O4-carrying composite PAN nanofibers-catalyzed Fenton-like system has been successfully developed for discoloration of an active commercial dye, Rhodamine B, in an aqueous solution. Through a number of experiments under various conditions, it was found that the reactivity of the system was influenced by catalysis dosage, temperature, the concentration of hydrogen peroxide, the pH, the initial dye concentration. The most important characteristic of heterogeneous Fenton-like processes is the formation of OH radicals, which are highly oxidative, nonselective, and able to decompose many organic compounds. Also, the advantages of the heterogeneous Fenton processes are complete mineralization of organic compounds at ambient temperature and easy separation of the heterogeneous catalysts from the treated wastewater. In our experiment, the catalysis can be used under moderate conditions (neutral and relatively low temperature) and recycled via magnetic adsorption. The Fenton-like catalysis could be repeatedly used many times still with high catalytic activity. In summary, the prepared Fe3O4-carrying composite PAN nanofibers exhibited excellent catalytic performance in the Fenton-like reaction towards degradation of the dye wastewater.