Preparation Of MnO₂Nanowires Based Electrode Materials And Their Supercapacitance Properties

Of the electrochemical capacitors, in the past years, the supercapacitors haveattracted global attentions. In comparison with conventional capacitors,supercapacitors have higher power density and longer cycle life, but their energydensities are still less than that of batteries. According to the energy density equationE=CV2, there are two effective methods can be used to improve the energy densityof supercapacitors, which one is getting higher work voltage with hybrid system andother one is developing nanostructure of electrode to enhance its specific capacitance.Our study focuses on the second approach. Three types of materials are presented forsupercapacitors include carbon-based, transition metal oxide-based and conductingpolymer-based.In this thesis, we provided a novel method to synthesize a composite structure ofα-MnO₂nanowires loaded on the surface of CMK-3for the first time. Otherwise,high-pure α-MnO₂nanowires material was also synthesized from as-prepared α-MnO₂nanowires/CMK-3composite. Furthermore, the electrochemical capacitanceperformance of these materials was investigated. The main contents are as follows:α-MnO₂nanowires/CMK-3composite was prepared with a two-steps method byusing Manganese acetate （Mn（CH3COO）2）, Potassium permanganate （KMnO₄） andCMK-3as the raw materials. Following, high-pure α-MnO₂nanowires product wassynthesized by the removing of CMK-3via a pyrolysis process under oxygenatmosphere. The products were characterized by X-ray diffraction （XRD）, scanningelectron microscopy （SEM）, transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HR-TEM）, and thermo-gravimetricanalysis （TGA）. The effects of various synthesis parameters such as reaction time,reaction temperature, concentration of chemical reagents, etc. were also thoroughlyinvestigated. It has been found that the preparation conditions have great effects onthe structure of the final product. The results also show that the C-O and–COOHcarboxylic functional groups on the CMK-3surface have effective effect to enhancing cycle life performance of the α-MnO₂nanowires/CMK-3compositeelectrode.