Hollow Materials And Electrochemical Properties Of Different Morphologies Were Prepared Manganese Oxide Etch Redox

Manganese oxides with hollow interiors have been widely applied in materials for supercapacitor, catalysts, ion exchange sieves, and adsorbent owing to their unique properties, such as high specific surface area, low density, good permeation, high specific capacitance and environmental compatibility. In this thesis, a variety of uniform manganese oxide nonspherical hollow materials have been prepared via a sacrificial template-engaged redox etching from the corresponding shape-controlled CU2O nanocrystals in KMnO4aqueous solution at room temperature, and the top-down redox etching process has been further researched. Moreover, the electrochemistry properties of as-prepared manganese oxide hollow structure electrodes with different morphologies have also been investigated.This thesis mainly consists of three sections, reviewer, experimental and conclusion. Introduction part (chapter1) reviews the structure, classification, propriety, preparation method and the application of manganese oxide. Experimental part (chapter2and chapter3) describes the preparation and the electrochemical property of a variety of amorphous manganese oxide material electrodes with different morphologies and uniform hollow structure. In chapter2, a variety of amorphous manganese oxide material electrodes with different morphologies and uniform hollow structure are prepared via sacrificial template-engaged redox etching route and the top-down redox etching process has been further researched. In chapter3, the electrochemical property of as-prepared manganese oxide hollow structure electrodes has been investigated by cyclic voltammetry and electrochemical impedance spectroscopy in1mol L-1Na2SO4solution in a voltage of-0.2-0.8V for three material electrodes. The research conclusion is finally described in chapter4.The manganese oxide hollow architectures with cubic, truncated cube, cubooctahedron, truncated octahedron, octahedral and star-shaped morphologies have been successfully prepared via sacrificial redox etching method by engaging of corresponding Cu2O templates. By using the suspension of Cu2O with different morphologies as precursores, a mixed solution of KMnO4and hydrochloric acid is dropped into the suspension and stirred for48h. The redox reaction occurs at the interfacial region, where the permanganate ions are chemical reduced by Cu2O and the corresponding manganese oxide hollow structures are simultaneously obtained. The redox etching process is carried out by a top-down pathway and the as-prepared amorphous manganese oxide hollow structures keep well the sizes and shapes of Cu2O corresponding nonspherical precursores. The structure, morphology and porosity property of the obtained materials are characterized by XRD, XPS, AAS, SEM, TEM and BET analyses.The electrochemical property of as-prepared amorphous manganese oxide hollow structure electrodes has been investigated by cyclic voltammetry and electrochemical impedance spectroscopy in1mol L-1Na2SO4solution in a voltage of-0.2-0.8V. The amorphous manganese oxide electrodes show a characteristic faradic capacitance behavior. Among these amorphous manganese oxide electrodes, the star-shaped amorphous manganese oxide electrode exhibits a high specific capacitance of366F g-1at a scan rate of5mV s-1, which is much higher than that of other five manganese oxide electrodes. The high capacitance is attributed to its large specific surface area (198m2g-1), which promotes the adsorption/desorption of protons or alkali cations from electrolyte and enhances the specific capacitance of obtained porous amorphous manganese oxide hollow structures.