Synthesis And Catalytic Properties Of Graphene-Supported Composite Catalysts

Graphene?GE?is an excellent support for catalyst preparation.Combining the advantages of both graphene and the catalytical active components,the graphene supported catalysts possess enhanced stability,improved electrical conductivity and electron mobility,as well as high available surface area.Moreover,these graphenesupported composite catalysts can significantly lower the over-potentials and facilitate the electron transfer between the analyte and the electrode surface,which play key roles in the design of high performance electrocatalysts.In this thesis,we have prepared several graphene-based binary catalytic materials,including graphene supported cuprous oxide?Cu₂O?hollow cubes,Co nanoparticles,hexagonal and cubic crystalline Ni nanoparticles,and studied their preparation methods,formation mechanisms,morphologies and microstructures and especially the catalytic applications in the reduction of 4-nitrophenol?4-NP?and glucose sensor.The main points are as follows:1.Cu₂O hollow cubes were synthesized on reduced graphene oxide?RGO?nanosheets by a facile one-pot refluxing approach.The as-prepared RGO/Cu₂O nanocomposites were characterized by X-ray diffraction?XRD?,Raman spectroscopy,transmission electron microscopy?TEM?,and X-ray photoelectron spectroscopy?XPS?.It was revealed that Cu₂O with well-defined hollow cubic morphology is homogeneously dispersed on the surface of RGO nanosheets.The electrocatalytic properties of the RGO/Cu₂O composites for glucose oxidation were investigated by cyclic voltammetry and chronoamperometry.It was found that the constructed glucose sensor has a wide linear range of 0.01⁹.0 mM?R2 = 0.997?with high sensitivity of 785.69 ìA cm-2 mM-1 and low detection limit of 0.44 ìM based on signal/noise = 3.Compared to bare Cu₂O and previously reported Cu₂O-based glucose sensors,the as-prepared RGO/Cu₂O glucose sensor showed remarkably enhanced electrocatalytic activity.In addition,the electrode also exhibited an excellent anti-interference ability.The excellent electrocatalytic performance together with the simple and low-cost preparation makes RGO/Cu₂O be attractive in glucose sensor application.2.Co nanoparticles with high dispersivity were in-situ grown on RGO nanosheets by an environmentally friendly and facile one-step strategy.The assynthesized products were characterized by Raman spectroscopy,XRD,TEM,and XPS.The magnetic and catalytic properties of the RGO/Co nanocomposites were systematically investigated.The results reveal that the RGO/Co nanocomposites have room-temperature ferromagnetic characteristics with Co particle size below single domain size.In addition,these RGO/Co composites also exhibit excellent catalytic activities toward the reduction of 4-nitrophenol by NaBH4 and enhanced electrocatalytic properties for the oxidation of glucose.3.RGO supported Ni nanoparticles were synthesized by a facile in-situ refluxing approach using triethylene glycol as both reductive and dispersing agent.The assynthesized RGO/Ni nanocomposites were characterized by XRD,Raman spectroscopy and TEM,which revealed that Ni nanoparticles with hexagonal closepacked structure were homogeneously dispersed on the surface of RGO sheets.The catalytic activity and electrochemical properties of the RGO/Ni nanocomposites were investigated.It is found that the RGO/Ni composites exhibit markedly enhanced catalytic activity toward the reduction of p-nitrophenol by NaBH4,which is comparable to noble metal catalyst.The RGO/Ni nanocomposites also exhibited excellent electrocatalytic response to glucose.The linear range,detection limit and sensitivity were estimated to be 0.01-3.0 mM?R2 = 0.997?,2.8 ?M and 535.258 ?A mM-1 cm-2,respectively.It is believed that this eco-friendly and facile route can be extended to synthesize other metal nanostructures on RGO nanosheets with various functions,and provides a new opportunity for the application of graphene/metal nanocomposites.4.GE nanosheets supported uniform-sized Ni nanocrystals were synthesized through a facile calcination process using metal-oleate complex as precursor.The assynthesized products were characterized by XRD,Raman spectroscopy,TEM,XPS and the Brunauer-Emmett-Teller?BET?analysises.The magnetic and electrocatalytic properties of the GE/Ni nanocomposites were systematically investigated.The results reveal that the GE/Ni nanocomposites have room-temperature ferromagnetic characteristics.The GE/Ni nanocomposites also exhibited excellent electrocatalytic response to glucose.The linear range,detection limit and sensitivity were estimated to be 0.01-2.5 mM?R2 = 0.997?,0.86 ?M and 358.0 ?A mM-1 cm-2,respectively.The synthetic procedure is not only easily scalable for mass production but also can be extended to synthesize other GE/metal nanocomposites,which can be potentially applied for catalysis and energy storage.