Preparation Of Graphene-based Fe / Ni Composites And Researching Their Performance Of Supercapacitors

Supercapacitors is a new energy storage device, its energy storage mechanism between the traditional capacitors and the conventional chemical batteries. Recently,the research focus on supercapacitor electrode material which can combine the double layer capacitor with Faraday Pseudocapacitance.Graphene and metal oxide nano-composite material as a capacitor electrode material has advantage of both the two materials, The large surface area and rich of oxygen-containing functional groups of graphene make it possible for the metal oxide nanoparticles in the graphene surface,and the metal oxide can use of its excellent conductive properties to achieve their own Faraday Pseudocapacitance, in addition the introduction of metal oxide nanoparticles,can reduced the van der Waals force between the graphene sheets inhibit its aggregation phenomena occur during charging and discharging, so that the graphene large specific surface area can preserved. In this paper, we researched the structural characteristics and capacitance performance of graphene & iron oxide nanoparticle composites and graphene nanoparticles & nickel oxide composites. The main content is divided into three parts:(1) Preparation and characterization of graphite oxide and graphene. Frist of all we use the modified legal Hummer method and natural graphite powder as raw material graphite oxide to prepared GO, and studied the impact of different amounts of potassium permanganate on the preparation of graphite oxide, the results showed that with the increases amount of potassium permanganate(from 3g to 6g), the diffraction peak of graphite oxide increases, when it reach a peak,the diffraction peak of graphite oxide began to decline and the rate of 1:1:5(natural graphite: mass ratio of sodium nitrate : potassium permanganate) is the best performance of preparation graphite oxide.Then we used high-temperature heat reduction method and green way to obtain graphene, the result show that use of sodium citrate reduction method obtained graphene have few defects than than high-temperature heat reduction method.(2)Preparation and supercapacitor performance of Fe3O4/G composites. WithFe Cl3 ? 6H2 O as iron source, graphite oxide as a precursor, ethylene glycol as a solvent and use one-step solvothermalmethod to synthetic iron oxide/ graphene composites. During the experiment we prepared four groups composites which the amount of iron oxide / graphene is diffent, and study their performance as an electrode materials. The results show that,composites specific capacitance is much larger than that of the iron oxide nano particles, and the composite FG1-2(The mass ratio of Fe Cl3 · 6H2 O and GO is 1: 2 for the preparation of composite materials named FG1-2) has the most superior performance and has a good cycle stability,when the scan rate is 5mvs-1,the specific capacitance is 236.4F/g, after 1000 cycles its specific capacitance remaining 93.1%.(3) Preparation and supercapacitor performance Ni O / G composites. With nickel nitrate hexahydrate nickel source, GO to graphene material, urea as a precipitant, first we use hydrothermalmathed to produce a composite precursor(GO/Ni(OH)2) and then under an argon atmosphere use high-temperature calcination to preparation of Ni O/G composites. During the experiment we prepared four groups composites which the amount of iron oxide / graphene is diffent, and study their performance as an electrode materials. The results show that, the composite specific capacitance much larger than that of the nickel oxide particles, and the composite 2 has the most superior performance(the mass of Ni(NO3) 2 and urea are 350 mg, 288 mg prepared material designated as composite 2),when the scan rate is 5mvs-1, its specific capacitance is 862.6F/g.