Preparation And Application Of Nano-Structured Manganese Oxides

As an important transition metal oxide, manganese oxides had been used widely in many fields such as battery materials because of its excellent redox characteristics. The applications of nano-sized Manganese oxides had been greatly expanded because of its special nanometer effect. Therefore, preparation of high-performance nano-structured manganese oxides and development of potential application had become a hot research. In this paper, manganese oxides nanosheets (MONS) and manganese oxides nanorods were prepared, and their application in electrochromic, catalytic and biosensor were studied, respectively.In this thesis, manganese nitrate had been as raw materials, manganese oxides nanosheets had been prepared by hydrothermal method and delaminating a layered protonic manganese oxide into colloidal single layers. An electrode of MONS film was prepared by layer-by-layer assembly. Electrochromic behavior of MONS film electrode had been studied in KCl electrolyte and an electrochromic mechanism had been obtained. In cyclic voltammeter (CV) measurement, the color of MONS film changed from light yellow to dark brown when CV swept in positive direction, and the color changed from dark brown to light yellow when CV swept in negative direction. Experimental results showed that electrochromism of MnO₂ were caused by valence changes of Mn and insertion/extraction of K⁺. The process of coloration was accounted for oxidation Mn3+ to Mn⁴⁺ of the MnO₂ associated with the insertion of K+ into the MONS galleries. The transformation of Mn4+ into Mn³⁺ and the extraction of K⁺ ions led to bleach of MONS film.In this thesis, potassium permanganate, manganese sulfate and copper sulfate had been as raw materials, copper-decoratedα- MnO₂ nanorods (CuO@α-MnO₂) had been synthesized facilely by a hydrothermal method. These new nanomaterials were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Based on the results of analysis, a formation mechanism of CuO@α-MnO₂ nanorod was obtained. The results showed that the formation process was a characteristic of a rolling mechanism and phase transformation ofδâ†'α-MnO₂. Catalytic properties of CuO@α-MnO₂ were studied on the decomposition of sodium hypochlorite. The results showed that CuO@α-MnO₂ nanorods had a high catalytic activity for decomposition of sodium hypochlorite, and the rate of decomposition was more than 99% in 5 min at temperature of 75℃, which provided the possibility of industrial applications.In this thesis, potassium permanganate and manganese sulfate had been as raw materials,α-MnO₂ nanorods had been synthesized by a hydrothermal method,and an electrode of manganese dioxide-gelatin / glassy carbon (MnO₂-gelatin/GCE) had been assembled. The properties of electrochemical response of MnO₂-gelatin/GCE electrode were studied on hydrogen peroxide using the catalytic properties of MnO₂. The results showed that the electrode prepared had an excellent response for hydrogen peroxide: response speed, high response current and low detection limit. The response time of the electrode was 6-7 s, the sensitivity was 32.5μA/cm²Â·mmol and the detection limit of the electrode was 1.9×10^-7 mol/L.