Preparation,Characterization And Applications Of Carbon-based Materials

Based on the excellent physical and chemical properties of new carbon materials, such as large specific surface area, excellent electrical conductivity, and stable chemical performance and so on, they can be widely used in many applications like environmental remediation, electrochemical and biological fields. Among them, graphene, carbon spheres and porous carbon are three typical representatives of carbon materials. In this thesis, we synthesized a series of carbon based nanocomposites aimed at these three typical carbon materials as matrix by using novel but simple synthetic methods, and study deep of the morphology, structure and their applications in wastewater treatment, supercapacitors, magnetic and catalytic fields. Hence, based on these, the main research contents of this thesis are summarized in the following points:(1). Since 2004, the discovery of graphene sets off a worldwide study boom of carbon materials again, and it has begun to exceed the carbon nanotube (CNT) and become a high-profile international frontier and hot aspect. Here, we also carried out the related research of graphene-based nanocomposites. a):We have reported a facile method for preparation of reduced graphene-BiFeO3 nanocomposite through the self-assembly decoration of the BiFeO3 nanoparticles on reduced graphene via a hydrothermal process for the first time. The structure, composition and morphology characterizations of the nanocomposite indicated that pure BiFeO3 perovskite phase was successfully processed, which anchored on the surface of reduced graphene sheets and had a good dispersion behavior, confirming that the technique in this paper acted as a good strategy. The magnetic and UV-Vis absorption spectroscopy measurement showed that the magnetization and optical activity of the nanocomposite was found to be changed to compare with those of the pure BiFeO3, which would be promising for more practical application in future nanotechnology. b):A novel hydrophilic RGO-CD-Ag hybrid with the supramolecular β-cyclodextrin (CD) as a conjugation interface was fabricated successfully by a facile in situ synthesis process.The results of several characterizations confirmed that the in situ reaction provided a straightforward approach to deposit the CD wrapped Ag nanoparticles onto the CD chemical functionalized RGO sheets through the head-to-head H-bonds interactions between the linker CD molecules. Moreover, it was also found that the CD interface existed indeed influence to the structure and performances of RGO-CD-Ag nanocomposite. The analysis of the static contact angle revealed the surface property of the hybrid that could be transformed hydrophobic into hydrophilic feature, which highly improved the aqueous dispersibility. And then, the bactericidal test of RGO-CD-Ag was demonstrated and clearly showed the strongest antibacterial activity against Gram-negative and Gram-positive bacteria among all samples. In short, this method may readily provide a new family of supramolecular-based materials to find applications used beyond bactericidal field. c):And now, a lot of research has been focused on nitrogen-doped graphene (NG), which has become a key-enabling technology to improve the properties of graphene through increasing its conductivity and surface active sites. Here, we demonstrated the preparation of nitrogen-doped graphene-CoO nanocomposites (NGC) by facile hydrothermal method and its application as a novel electrode material for supercapacitors for the first time. The results of several characterizations showed that NGC electrode exhibited enhanced capacitive performances relative to those of undoped graphene-CoO nanocomposites (GC). As the scan rate increased from 5 to 100 mV/s, the capacitance of NGC still retained～67%, which was considerablely higher than that of GC (44%). Moreover, over 77% of the original capacitance was maintained after 1000 cycles, indicating a good cycle stability of NGC electrode materials.(2). Among different forms of carbon materials, carbon spheres (CSs) have attracted considerable attention, owing to their potential wide variety of applications. Many approaches have been developed towards these nanostructured carbons, such as chemical vapour deposition, pyrolysis of carbon sources and catalyst, an arc plasma technique, and mixed-valence oxide-catalytic carbonization. However, each of these methods has its own advantages and limitations. To our knowledge, high reaction temperature or complex reaction process is required for these complex approaches.The use of cheap, non-toxic and low-energy materials as the carbon source for the preparation of various materials is a very important goal for synthetic chemists. So it is also worth to develop simpler and low-cost procedures to obtain CSs with a homogeneous construction and composition under the mild conditions. a):We report for the first time a facile and efficient strategy to prepare carbon microspheres by the carbonization of glucose in the presence of graphene under hydrothermal environment. The morphologies characterizations of the as-synthesized products confirmed that the technique in this paper acted as a good strategy, which a great deal of carbon microspheres with good morphology and uniform diameter were prepared. The chemical and structure characterizations indicated that there were many functional groups on the surface while the core was mostly amorphous structure with high purity. A formation mechanism was proposed that involved curved graphene sheets as a substrate for microsphere formation. As this route is low-cost, green and simple, and the experimental parameters are very easy to control, it may provide a great convenience to study properties and applications of carbon microspheres. b):A novel montmorillonite supported carbon nanospheres adsorbent (MMT@C) was fabricated successfully by a green and facile technique called hydrothermal carbonization, which was used to removal Cr(VI) aqueous solution. The batch adsorption results showed that, when the adsorption equilibrium time was 60 min and the optimum adsorption pH was 2, this novel MMT@C adsorbent exhibited excellent performance (156.25 mg/g) for the removal of Cr(VI), which was much higher than raw Mt and the previously reported values of other materials. Kinetic and isotherm studies showed that Cr(VI) adsorption was more favorable at higher concentration and monolayer adsorption occurred on the adsorbents. Therefore, it can be suggested that this novel MMT@C nanocomposite could be a good candidate for removing Cr(VI) from wastewater, and this research provides a new route for the development of new environmental remediation nanomaterials.(3). Porous carbon oxide (PC oxide) was firstly prepared by the modified Hummer’s method which used to prepare the graphene oxide ago. The structure and properties of PC oxide were analyzed with TGA, FTIR, XRD, BET and SEM. The electrochemical properties were detected by the cyclic voltammetry method and the differential pulse voltammetry method. The results show that the PC oxide not only maintained the basic parameters of the porous structure and better solubility in water, but also has better capacitance performance, which benefited from the enhanced pseudo-capacitance effect generated from the increased oxidation functional groups on the surface of the open-framework structure.