The Preparation Of Metal Oxide/Graphene Composite Materials And Their Application In Catalytic Oxidation

Graphene is a two-dimensional one-atom-thick carbon material, which aroused an intensive interest in the domain of electronics, energy, photonics and catalysis for its unique feature of specific surface area since its revolutionary discovery. This novel material is an ideal substrate for supporting catalytic species and has been successfully made with inorganic nanostructures, organic crystals, polymers and biomaterials. Recently, graphene-based composites, in particular, metal oxide/graphene composites have been widely used in lithium batteries, sensors, photocatalysis and other fields. However, the applications of metal oxide/graphene composites in the chemical catalytic reaction are rarely reported. And yet, the application of metal oxide/graphene possesses significant value in academic research, espacially in organic chemistry and industry as well.In this paper, graphene oxide, the precursor of graphene, was synthesized by modified Hummer method, and two kinds of metal oxide/graphene nanocomposites with highly efficient catalytic oxidation ability were respectively obtained.First of all, the SnO2/RGO composite was prepared via in situ hydrothermal strategy and detected by XRD, FTIR, XPS, TEM and TG. The epoxidation of cyclohexene was taken as probe reaction to evaluate the catalytic efficiency of the SnO2/RGO nanocomposite. The optimized reaction conditions were detemined through single-factor parallel experiment and the epoxide selectivity was improved up to 98.2% with a conversion of 92.5%.11 different alkenes were introduced to investigate the generality of this catalytic system, and four steps’ plausible catalytic cycle was also proposed, inferring that the substrates with electron-donating groups would more easily be epoxidized. Besides, a series of different metal oxides and some other solid supported catalysts like SnO2/SiO2, SnO2/Graphite were introduced and prepared, showing that graphene-based composite exhibited much better catalytic performance than traditional counterparts. Finally, the recyclability was further studied through circulation experiment using cyclohexene as substrate and both conversion and selectivity could still be higher than 90% after catalyst recycled for 10 times. The SnO2/RGO nanocomposite is truly heterogeneous and fairly stable with no active species leaching, which has promising industrial applications.On the other hand, WO3/RGO nanocomposite doped with metal Cs (Cs-WO3/RGO) was successfully prepared for the first time in our experiment and characterized the materials through XRD, FTIR, TEM and TG. Then the successful growth of Cs-WO3 with 10nm and 6-8nm wide nano square structure was obtained via one step hydrothermal method. The nanocomposites showed remarkable catalytic properties on the selective oxidation of benzyl alcohol compared to those unsupported or undoped particles, and the conversion and selectivity were 91.2% and 91.6% respectively under optimal reaction conditions. In addition, the composite had a good stability, the selectivity was basically unchanged and the conversion was over 80%, even after the catalyst reused 5 times.