Synthesis And Application Of Novel Carbon-based Catalysts

Graphene has high surface area, Young's modulus and the quantum Hall effect. It has high electron mobility even at room temperature. At the same time, another significant characterization of graphene is that its electronic structure is sensitive to external environment; and external electronic (magnetic) field, mechanical deformation, chemical modification, doping and even adsorbed other molecules or materials may modulate its electronic properties. At present, the research and application of graphene in supercapacitors, new energy batteries, microelectronic circuits and other areas is now in full swing. Meanwhile, new discoveries and results will emerge in endless.^In addition to its varied physical properties, we believe that the electronic proteries of graphene have advantages in catalysis reations and graphene also has many potential applications, which attribute to that the key stages of catalysis reactions (such as adsorption of reactants, surface diffusion of chemisorbed molecules, and formation of new chemical bonds between surface adsorption of reactants and desorption of species, etc.) depend on the electron transformation between catalysts and reactants. Moreover, the surface valence electrons structure of catlaysts affect the activation energy barrier of reactants (corresponding to the activity) and the reaction path (corresponding to selectivity).Therefore, graphene could be good supports. And exploring these novel materials in heterogeneous catalysis reactions has important academic signicance and application prospect. The main purpose of this thesis is to develop effective methods to explore easy and efficient nanomaterials and the application in relevant catalysis fields.First, this thesis showed that reduced graphene oxide supported platinum nanoparticles catalyst (Pt/rGO) was prepared via ethylene glycol (EG) reduction, which was used for the selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) in various solvents. It was found that the selectivity of COL remained 85.3% at 97.8% CAL conversion in ethanol. The prominent activity of Pt/rGO was attributed to that highly dispersed Pt NPs, micropore-free structure of Pt/rGO (contaction on both sides of graphene) and well dispersion of Pt/rGO and substrates in reaction mixture in ethanol.Next, the third chapter of this thesis explored the activity of the selective hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) over reduced graphene oxide supported platinum catalyst (Pt/rGO) compared with those of Pt supported over varied supports catalysts. The influence of varied reaction parameters, such as solvent, reaction temperature, H2 pressure, HMF concentration, stirring speed and other parameters of the reation were also investigated. It was found that the yield of DMF reached 73.2%with a 100% conversion of HMF at 120?,3.0 MPa H2 and 2.0 h in 12 mL butanol.The prominent performance of Pt/rGO could be attributed to the micropore-free structure of Pt/rGO, PtNPs dispersed highly on both sides of rGO, the selective adsorption of HMF, and so on.The fourth chapter of this thesis explored different synthetic process of Pt3Co alloy catalysts. It was found that microwave irradiation-assisted reduction method had many advantages, such as higher metal utilization, the easy control of alloy composition, improved dispersion of Pt3Co particles and minimizing re-graphitization of the parents rGO compared with convertional solvent-thermal and impregnation methods. Moreover, the highly dispersed and unique Pt3Co particles (-2.3 nm) were obtained via microwave irradiation-assisted reduction method, and Pt3Co/rGO-MW catalyst was extremely active and selective for the hydrogenation of CAL to COL.In order to impove the activity and stablility of metal nanoparticles over graphene, the fifth chapter of this thesis reported a pyramid shaped alloy-metal oxide-graphene hybrid that was synthesized via microwave irradiation-assisted reduction method, in which SnO2 nanoparticles (NPs) (4.8-5.8 nm) were first coated onto the surface of reduced graphene oxide (rGO), and then very fine Pt3Sn NPs (0.6-1.2 nm) were fabricated on the surface of SnO2-rGO. This pyramid shaped Pt3Sn/SnO2/rGO hybrid was highly active, selective and stable for hydrogenation of C=O bond in unsaturated aldehydes to unsaturated alcohols under mild conditions.The sixth chapter of this thesis reported graphene encapsulated Fe3C that embedded in carbon nanotubes catlaysts (denoted as Fe3C@G-CNT) were synthsized via direct pyrolysis of renewable biomass (glucose, xylitol and sucrose), melamine and FeCl3. Detailed characterizations results indicated that the morphologies and properties of Fe3C@G-CNT composites depended strongly on pyrolysis temperature. It was found that Fe3C@G-CNT-700 (prepared at 700?) catalyst had high graphitization, well defined and controllable structure of CNTs, and was highly active and stable for the hydrogenation of nitroarenes and C=C bond in several compounds. Aboved results showed that full contacts between molecules and Fe3C in a restricted area promoted activity and graphene encapsulated Fe3C improved the stability. According to the above synthetic process, graphene encapsulated Ru nanoparticles supported on carbon sheets catlaysts (denoted as Ru@G-CS) were synthsized via direct pyrolysis of glucose, melamine and RuCl3.It was found that Ru@G-CS-700 (prepared at 700?) catalyst had highly dispersed and unique Ru particles (2.5±1.0 nm), and was highly active and stable for the hydrogenaiton of these unstable components in bio-oil even in aqueous media. It was found that carbon sheets imporved the dispersion of Ru nanoparticles and ultrathin N-doped graphene encapsulated Ru nanoparticles improved stability of catalyst.In conclusion, this thesis has carried out the preliminary exploration on both the preparation and application of novel carbon-based functional nanomaterials, which provides new experience to extend new carbon-based applicatios.