Preparation And Electrochemical Properties Of New Carbon/Manganese Dioxide Composites

In recent years,supercapacitor has been widely studied and applied as a charge storage device with high power density,excellent reversibility and recyclability.Most of the research in this field is focused on the development of different electrode materials,such as various forms of carbon materials,conducting polymers and transition metal oxides.Of all these materials,transition metal oxide manganese dioxide is considered to be a promising supercapacitor material for low-cost and environment-friendly asymmetric EC devices with high specific capacitance.However,the conductivity of pure manganese dioxide electrode materials is poor and based on Faraday reaction,which greatly affects the specific capacity and cyclic stability of the electrode.Therefore,it is possible to optimize the electrochemical properties of nano-manganese dioxide in a carbon scaffold with high conductivity and high ratio surface.Based on the advantages of manganese dioxide and carbon material structure,a series of manganese dioxide based composite electrode materials were designed and prepared,and its structure and electrochemical properties were studied.The main contents and results of the paper are as follows:?1?Study on the preparation and electrochemical properties of reduced graphene oxide/manganese dioxide?rGO/MnO₂?composite materials by hydrothermal methodUsing potassium permanganate and graphene oxide?GO?as raw materials,the electrode materials with different morphology were obtained by adjusting the amount of potassium permanganate and GO reduction.Structural analysis shows that the remaining oxygen-containing functional groups in rGO have inhibitory effect on the crystallinity of manganese dioxide,and inhibits the large amount of manganese dioxide from growing up,which contributes to the improvement of material capacitance.At the same time,when the amount of potassium permanganate is reduced,manganese dioxide presents lower crystallinity but larger capacitance,the specific capacitance of the composite reaches 169 F g^-11 under the current density of0.2 A g^-1,the specific capacitance of MnO₂ in the composite is about 215 F g^-1,which is superior to composite materials prepared by other synthetic conditions.?2?Study on the preparation and electrochemical properties of carbon made from metal-organic frameworks/manganese dioxide?MOF carbon/MnO₂?composite by redox methodThe active carbon material SZC with unique pore structure was synthesized in the inert atmosphere by using MOF as the precursor,and the activated carbon material ASZC as the control group were prepared by KOH activation method.Activated carbon/manganese oxide composite materials were prepared by redox reaction at normal temperature.The result analysis shows that the electrochemical properties of carbon materials are significantly improved after activation,the specific capacitance of SZC carbon materials was 50 F g^-11 under the current density of 1 A g^-1,specific capacitance of ASZC carbon material increased to 103 F g^-11 after activation,but activation damage the structure of carbon materials,which reduce the conductivity of the carbon material,meanwhile its electrochemical properties were worse instead after compound with MnO₂.Among them,the specific capacitance of SZC/MnO₂composite material was 159 F g^-11 under the current density of 1 A g^-1,and when the current density is increased from 0.3 A g^-11 to 2 A g^-1,and the capacitance still retains76.7%of its initial capacitance,showing a high magnification performance.?3?Study on the preparation and electrochemical properties of reduced graphene oxide/carbon dots/manganese dioxide?rGO/CDs/MnO₂?composite nano-material electrode materialsWe systhesized carbon points with small particle size under intermediate temperate?500 ^oC?,upon carbon dot in situ compounded with GO and was inserted into the interlayer,rGO/CDs material with unique structure was prepared after hydrothermal reduction,rGO/CDs/MnO₂ ternary composite nano electrode material was prepared by the reaction of rGO/CDs and potassium permanganate.The results analysis revealed that the addition of carbon points solved the problem of the aggregation of GO after reduction perfectly,while the addition of potassium permanganate was 5 mmol,the composite had the best electrochemical properties.When the current density is 0.3 A g^-1,the capacitance of composite could be up to 221 F g^-1,and the current density was increased from 0.3 A g^-11 to 2 A g^-1,and the capacitance still maintained 79.2%.