Preparation And Electrochemical Properties Of Low-defect Graphene Based On Sheet-clustered MgO

With the rapid development of global economy and technology,the development of sustainable and efficient clean energy and new technologies related to energy conversion and storage has become the main focus of industry and science.Supercapacitors(SCs),as high-performance energy storage devices,have the ability of real-time power supply and maintaining millions of cycles of charge and discharge at higher current density,so they have attracted much attention of researchers.Graphene has a good application prospect in supercapacitors because of its excellent physical,chemical and electrical properties.But,in the chemical vapor deposition(CVD)in the process of preparation of graphene,there are still some problems,such as growth in the catalyst metal surface,need to carry on the transfer process,due to the difference of substrate material,the preparation of graphene performance difference is bigger,low yield,defect is more,secondly as electrode materials,graphene actual specific capacity is far lower than the theoretical value and so on,these questions restrict its application.Based on this,a series of graphene samples with different morphologies and defects were prepared by CVD method using different piece of clusters of magnesium oxide(MgO)and modified CuO/MgO composites as substrates.Their morphologies and structures were characterized,and their electrochemical properties in supercapacitors were compared.The main research contents and results of this paper are as follows:1.Three different kinds of magnesium oxides were used as substrate materials to prepare graphene by CVD method.The morphology and structure of graphene were characterized by scanning electron microscopy(SEM),powder X-ray diffraction(XRD)and microconfocal laser Raman spectrometer(Raman).Secondly,the prepared graphene was respectively used as electrode material and conductive agent to assemble the supercapacitor,and the electrochemical performance tests such as cyclic voltammetry(CV),alternating current impedance(EIS),constant current chargeand discharge(GCD),and cyclic stability were carried out using the electrochemical workstation and battery testing system.The results show that when the CVD reaction temperature is 950?,the reaction time is 60 min,and when the MgO with loose lamellar structure is used as the substrate,the yield of graphene prepared is higher and the defect is lower.The prepared graphene can not only be used as electrode material but also can be used as conductive agent in supercapacitors,and shows better electrochemical performance than conductive carbon black.2.The MgO substrate was modified by adding copper element to prepare CuO/MgO composite,which was used as the substrate material to prepare graphene with low defect by CVD method.The morphology and structure of CuO/MgO composite and graphene were characterized by scanning electron microscopy,powder X-ray diffraction and micro-confocal laser Raman spectrometer.Compared with unmodified MgO,CuO/MgO composite substrate added with Cu element can reduce the defects of graphene and also reduce the temperature of graphene formation,which has a good development prospect.In this work,since the method of completely removing the substrate material in the prepared graphene samples has not been found,the performance of graphene in supercapacitors needs to be further studied.