Research On Preparation And Supercapacitive Properties Of Graphene

Graphene is a kind of novel carbon material, which was successfully preparedin2004. This new type of new material has been paying great attention due to itsunique mechanics, themal, opticals and electronics properties. The chemical methodsare thought to be the effective way of producing graphene with high-performanceand low-cost. In this thesis, graphene were synthesized by the normal themalexfoliation and microwave-induced exfoliation of graphite oxide, and further studyon the method of alkali activation of graphene with KOH, and supercapacitiveproperties of obtained activated graphene was investigated.Graphite oxide was prepared using ultrafine graphite powder by Hummersmethod. The obtained graphite oxide and super fine graphite powder wascharacterized by X-ray diffraction, fourier transform infrared spectroscopy, scanningelectron microscope and laser particle size analyzer. The results show that theaverage particle size of ultrafine graphite powder is5.20micrometer, internaloxidation increased the distance between the layers of graphite from0.336nanometer to1.06nanometer, which was induced by the oxygen-containingfunctional groups.Graphene was obtained by the normal themal exfoliation of graphite oxide at150℃,200℃and300℃in normal atmosphere. The composition and morphologyof the graphene nanosheets were studied with X-ray diffraction, fourier transforminfrared spectroscopy, scanning electron microscope, transmission electronmicroscopy and selected-area electron diffraction(SAED), while the supercapacitiveproperties of the supercapacitor were investigated by using cyclic voltammetry (CV),galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS)techniques. The results show that the maximum specific capacitance of thesupercapacitor is about276F/g in6mol/L KOH aqueous electrolyte and exhibitsgood high-current charge-discharge performance. The graphene produced bymicrowave-induced exfoliation also exhibit good supercapacitive performance.The graphene were activated with potassium hydroxide at800℃under theprotection of the inert gases. The porous characteristics of the obtained activatedgraphene was observed by scanning electron microscope，and the specific surfacearea was1310m2/g. Supercapacitors were assembled by using activated graphene for electrode materials, and supercapacitive properties of the supercapacitor wereinvestigated by using cyclic voltammetry (CV), galvanostatic charge-discharge andelectrochemical impedance spectroscopy (EIS) techniques. The results show that atdifferent scan rates showed good characteristics of electric double layer capacitor,and exhibits good high-current charge-discharge performance.