Synthesis CNC-MnO₂Hybrid And Investigation On Electrochemical Performance

Supercapacitors, a sort of energy storage devices, exhibit novel and efficient charge-discharge power capability and efficiency, large power density, low maintenance cost. These excellent properties make supercapacitors suitable for wide applications. The main researches focused on supercapacitors are synthesis of electrode materials. At present, carbon-based active materials, metal oxides and conducting polymers are used as the electrode materials in supercapacitors. However, lack of capacity, poor electrochemical stability and environment pollutions restrict the applications of supercapacitors. The purpose of this thesis is to synthesize a kind of carbon nanocoil (CNC)/manganese dioxide (MnO2) composite material as the supercapacitor electrode, which shows excellent stability, low resistance, high specific capacitance and environment friendliness. CNCs have many outstanding properties due to their peculiar three-dimensional morphology, such as field emission properties, mechanical properties, electric properties, electrochemical properties and uniform dispersion. MnO2also have excellent properties, such as high pseudocapacitance and low resistance. The CNC/MnO2composite could obtain good performance by synergistic integration of the two nanomaterials. Both the lower electrochemical capacity of the CNC and the poorer stability of the MnO2can be neglected.In this thesis, a facile and efficient hydrothermal approach has been developed to synthesize three dimensional hybrid of Mno2and CNC as a kind of electrode material for supercapacitors. We studied the influence of surface treatment on the synthesis of CNC/Mno2composite. It is found that5M HNO3is beneficial to grow nanowiskers Mno2on the surface of CNC. This hybrid was prepared by anchoring uniformly porous MnO2nanowiskers over the surface of CNC. The electrochemical properties of CNC/MnO2electrode have been measured by a three electrode configuration, which exhibited high specific capacitance with values up to387F/g at a scan rate of10mV/s, whereas the specific capacitance of pristine CNC was40F/g in the same situation. These results suggest that the CNC/Mno2hybrid is comparable or superior to other carbon-based materials coated with Mno2nanowiskers. The CNC/Mno2composite has been the most promising candidate as supercapacitor electrode due to excellent electrochemical properties.