| Graphene has been emerging as a fascinating material because its remarkable structural flexibility, high electronic conductivity, superior thermal stability, large specific surface area and wide-spread potential applications in energy, environment, nanoelectronics and nanodevices. The combination of these attractive properties of graphene with the excellent characteristics of other functional nanomaterials has become a popular pathway for achieving applications in multiple fields. In this paper, we try to develop new methods to fabricate graphene-based binary and ternary nanocomposites with controlled shape and size, study the formation mechanism of the graphene-based nanocomposites, and explore their potential applications in many fields such as photocatalysis, supercapacitor and the reduction of4-nitrophenol (4-NP). The main points are as follows:1. A novel Ag2O/GO (GO=graphene oxide) nanocomposite as a visible-light induced photocatalyst has been fabricated by a simple solution route. The electrostatic interaction between positively charged Ag+and negatively charged GO sheets is responsible for the formation of Ag2O/GO nanocomposite. The well anchoring of Ag2O nanoparticles on the GO nanosheets was verified by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Photocatalytic degradation of Methylene Blue (MB) under visible-light irradiation was conducted to evaluate the photocatalytic performance of the Ag2O/GO nanocomposites. Due to the enhanced adsorption performance, smaller size of Ag2O nanoparticles and improved separation of electron-hole pairs after incorporation with GO sheets, the Ag2O/GO nanocomposites show enhanced photocatalytic activity compared with bare Ag2O nanoparticles. In addition, the kinetics of the photocatalytic degradation reaction and a detailed photocatalytic mechanism were also proposed. Our study paves a way to design highly efficient visible-light responsive photocatalysts for the removal of organic pollutants for water purification.2. Two different strategies, including in situ growth and self-assembly approach, have been developed to load CeO2nanoparticles onto reduced graphene oxide (RGO) nanosheets. The microstructure and morphology of the as-synthesized RGO/CeO2 nanocomposites were investigated by XRD, Raman and TEM. The results revealed that CeO2nanoparticles with well-controlled size and a uniform distribution on RGO sheets with tunable density can be achieved through the self-assembly approach. The significantly enhanced photocatalytic activity of the RGO/CeO2nanocomposites in comparison with bare CeO2nanoparticles was revealed by the photocatalytic degradation of MB under simulated sunlight irradiation, which can be ascribed to the enhanced separation of electron-hole pairs and enhanced adsorption performance due to the presence of RGO. A suitable loading content of CeO2on RGO was found to be crucial for optimizing the photocatalytic activity of the nanocomposites. It is expected that this convenient assembly approach with high controllability can be extended to the attachment of other functional nanoparticles to RGO sheets, and the resultant RGO-supported highly dispersed nanoparticles are attractive for catalysis and power source applications.3. RGO/CeO2nanocomposites with improved capacitance performance were designed and synthesized by a facile two-step approach, the assembly followed by thermal annealing process. The structure, morphology and composition of the resulting RGO/CeO2nanocomposites were studied systematically. The presence of RGO can prevent the aggregation and control the structures of the CeO2nanocrystals in annealing process. The nanocomposites were used as electrode materials for supercapacitor application. We demonstrate that it is capable of delivering high specific capacitance of265F g-1at a scan rate of5mV s-1with excellent cycling stability. The enhanced high-rate electrochemical activity may be ascribed to the synergetic effects between RGO and CeO2. The excellent power performance offer great promise for applications in electrode material for supercapacitors.4. A facile and general method was developed for the first time to synthesize a variety of semiconductor quantum dots (SQDs) supported on reduced graphene oxide (RGO) sheets, including RGO/metal oxides and RGO/metal sulfides nanocomposites. The obtained nanocomposites were investigated by Raman spectroscopy, XRD, Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS) and TEM. It was found that by using octadecylamine (ODA) as both reductive and dispersing agent, the resulting metal oxides and sulfides SQDs were all homogeneously deposited on the surface of RGO sheets. The optical properties of the as-synthesized RGO/SQDs nanocomposites were studied through Ultraviolet-visible (UV-vis) and photoluminescence (PL) spectroscopy. To demonstrate one potential application, the RGO/NiO nanocomposites were used as electrode materials for electrochemical supercapacitor, which exhibit enhanced capacitive activity and long cycle life. It is expected that our prepared RGO/SQDs nanocomposites could serve as promising candidates for power source, catalysis, optical sensitizer and optoelectronic applications.5. We developed a facile two-step approach to disperse noble metal (Pt, Au and Ag) nanoparticles on the surface of CeO2functionalized reduced graphene oxide (RGO) nanosheets. It was shown that Pt, Au and Ag with average diameters of about5,2and10nm are well dispersed on the surface of RGO/CeO2. The reduction of4-NP to4-aminophenol (4-AP) by NaBH4was used as a model reaction to quantitatively evaluate the catalytic performance of the as-synthesized RGO-based ternary nanocomposites. In such triple-component catalysts, CeO2nanocrystals provide unique and critical roles for optimizing the catalytic performance of noble metallic Pt, Au and Ag, allowing them to express enhanced catalytic activities in comparison with RGO/Pt, RGO/Au and RGO/Ag catalysts. In addition, a possible mechanism for the enhanced catalytic activities of the ternary catalysts in the reduction of4-NP was proposed.6. A three-component composite composed of RGO, Fe3O4and Ag nanoparticles was designed and synthesized by a simple and environmentally friendly strategy. It was shown that Ag and Fe3O4nanoparticles are uniformly dispersed on the surface of RGO sheets. Magnetic studies revealed a room-temperature superparamagnetic behavior of the RGO/Ag/Fe3O4nanocomposites. The results revealed that the presence of Fe3O4not only has a great influence on the size of the Ag nanoparticles formed on RGO, but also can significantly improve the catalytic activity and stability of them towards the reduction of4-NP. Moreover, after completion of the reaction the nanocomposit catalysts can be easily re-collected from the reaction system by a magnet. Possible mechanisms for the reduced size of Ag nanoparticles and the enhanced catalytic performance of RGO/Ag nanocomposites after combining with Fe3O4were proposed. The facile synthesis of RGO/Ag/Fe3O4nanomaterials together with their superior magnetic and catalytic performance provides a potentially new approach for the design and construction of graphene-based ternary nanostructured composites with various functions. |
PDF Full Text Request