Preparation Of Molten Iron And Nickel Graphene Research And Capacitive Properties Of Talc

With the worsening fossil energy depletion, there is an urgent need for new energystorage devices with high energy densities and power densities. Supercapacitors attractgreat interest as energy-storage devices, owing to its fast energy delivery, high powerdensity, and long durability. Graphene nanosheet (GNS) has exceptionally high surfacearea and superior electronic transportation properties, which makes it much promisingto the application as electrochemical double-layer capacitor; Layered double hydroxides(LDHs) containing transition metals are also promising electrode materials forsupercapacitors due to their moderate reaction conditions, low cost, high redox activity,and environmentally friendly nature. In this paper, we have studied the preparation andthe capacitance performance of GNS, Ni2+-Fe3+layered double hydroxides(NiFe-LDHs), and GNS/NiFe-LDHs composites, respectively. Details are asfollowing：(1) An improved Hummers method was used to the synthesis of graphite oxide(GO). By optimizing the preparation conditions, GNS-2with a high surface area up to818.03m2/g was prepared. The results of galvanostatic charge/discharge demonstratedthat its specific capacitance of186.9F/g at a current density of0.1A/g, and96.2%ofspecific capacitance retained after2000cycle test at a current density of5A/g.(2) NiFe-LDHs was prepared by hydrothermal synthesis method. NiFe-LDHs-1and NiFe-LDHs-2were prepared by optimizing the reaction conditions. Electrochemicaltests showed that both of them exhibited pseudocapacitance performance, but itsconductive properties and cycle stabilities were poor. By comparison, NiFe-LDHs-2hada better capacitance performance with a capacitance value of1017F/g at a currentdensity of0.5A/g. After500cycle test at a current density of2A/g, the specificcapacitance retention rate was49.6%.(3) A series of GNS/NiFe-LDHs composites were fabricated by hydrothermal synthesis method. Electrochemical tests demonstrated that the introduction of GNSimproved the electrochemical performance of NiFe-LDHs, especially, the specificcapacitance and cycle stability. GNS/LDHs-2composite exhibited the best capacitanceperformance with specific capacitance of1448F/g at the current density of0.5A/g.Andthe specific capacitance retention rate was66.3%, after500cycle test at a currentdensity of2A/g.