Synthesis Of Cobalt Oxide And Graphene Composite Materials And Their Electrochemical Performance For Supercapacitors

As a new type of energy storage devices, supercapacitors (also called electrochemicalcapacitors) have drawn much attention because of their high power density and excellentcycle stability performance. Owing to its high theoretical capacitance, cobalt oxide (Co3O4)has become a hot spot among many faradaic pseudocapacitance materials. Meanwhile, sincegraphene was found in2004, it was widely used as the electric double layer capacitormaterials because of its excellent conductivity and high specific surface area. Therefore,combining Co3O4with graphene is an effective way to improve the electronic conductivity ofCo3O4and thus improve its electrochemical capacitive performance.In this work, we first explored the capacitance properties of cobalt oxide. Cobalt oxidewas deposited on nickel foam via successive ionic layer adsorption and reaction (SILAR)method by adjusting the cycle times to change the loading mass and by calcinating to changethe crystal form. We used electrochemical performance test to explore the effect of theoptimum mass loading and morphology of cobalt oxide on the capacitance. It was found thatamorphous structure is more benefical for the specific capacitance.Secondly we explored the influence of the reduced graphene oxide with differentreduction degrees on the capacitance. Graphene oxide was prepared from natural graphitepowder by a modified Hummers method. We used fast thermally reduction andelectrochemical method to obtain reduced graphene oxide. We investigated the effects ofoxygen content、disorder degree、BET specific surface area as well as interlayer spacing onelectrochemical performance through a variety of characterization methods such as EPMA,FT-IR, XPS, XRD, Raman and BET.Finally, we prepared metal oxide/reduced graphene oxide composites via a chemicalprecipitation approach used ammonium as precipitator and subsequent calcination in Aratmosphere.We further prepared the binary transition metal oxide/reduced graphene oxidecomposites to explore the optimal combination and mass ratio of the binary metallic oxides onthe influence of capacitive performance.The research conducted in this paper has a certain guiding significance for preparation ofcapacitive materials and improvement of specific capacitance.