Dissertation > Industrial Technology > Electrotechnical > Electrical > Capacitor

EQCM Study on Electrodeposition Mechanism of Manganese Dioxide and Its Electrochemcapacitance Behavior

Author ZuoZuo
Tutor ZhangJianMin
School Zhengzhou University
Course Physical and chemical
Keywords Electrochemical quartz crystal microbalance Electrodeposition Electrolytic manganese dioxide Electrochemical Capacitance
Type Master's thesis
Year 2011
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Supercapacitor is also known as electrochemical capacitors, with a high capacity and high energy density than other characteristics, the power in the electronic device is widely used in recent years, many researchers conducted extensive research. Supercapacitors research mainly focused on two aspects: (1) preparing high-performance capacitor electrode material; (2) Preparation of capacitor electrodes. In order to obtain higher capacity, many researchers research to metal oxides, mainly ruthenium oxide, iridium oxide, and manganese. Among these metal oxides, manganese dioxide is inexpensive, environmentally friendly and abundant raw materials, and manganese dioxide having a crystalline structure and a variety of multiple oxidation states are widely used as redox supercapacitor electrode materials used in the energy storage device. Current research workers synthesized using different methods with good capacitive manganese oxide supercapacitor electrode material. Manganese oxide electrode materials for supercapacitors is mainly divided into two categories: one category is manganese oxide film, a class is a manganese oxide powder. Can be prepared in different ways structurally different morphologies obtained manganese oxide and manganese oxide with different morphologies structures capacitive properties of the super capacitor is different. Manganese dioxide can be prepared by chemical and electrochemical methods. The experimental electrochemical methods, were prepared by changing the experimental conditions different crystal manganese dioxide. In acidic electrolytes, electrolytic oxidation Mn2 can generate γ-MnO2. Acidic electrolytic manganese dioxide generated should be widely battery cathode material. The electrolytic oxidation in neutral medium Mn2 generate δ-MnO2, studies on δ-MnO2 is far less than the γ-MnO2 research. Electrochemical quartz crystal microbalance (EQCM) is a very sensitive quality testing equipment, precision Dana Ke level. The quartz crystal surface mass change into a crystal oscillation circuit output signal frequency changes according to the Sauerbrey equation change in frequency through the electrode surface changes in quality can be obtained. Potential measured with EQCM week after cycles generated Mn02 quality found in the neutral medium quality electrolytic oxidation of Mn02 increased 131.61μg, in acidic media increased mass 42.27μg. The test data show that the deposition rate in neutral solution is much larger than the deposition rate of the acidic electrolyte solution, the pH of the electrolyte Mn02 size is an important factor in the deposition rate. Crystal structure of manganese dioxide and a variety of different types of manganese dioxide crystals having different crystal structures, but they are in octahedral Mn06 the structural unit connected to different types of tunnel structure, the outer structure of the water molecules normally easily be embedded to manganese dioxide tunnel structures. This study investigated the δ-MnO2 in 0.1 M Na2S04 solution capacitance performance, cyclic voltammetry tests before the initial mass of MnO2 199.7μg, scanning electrochemical window is 0-0.8v, the oxidation process in the whole electrode active material continuous quality reduced by about 12.10μg, when the reverse scan quality and increasing, and finally back to the starting point, close to the initial value, indicating that the oxidation process of this cycle and the reduction process the same amount of mass change, these data indicate that electrode material during forward and reverse scanning ion intercalation and extraction is reversible. EQCM quartz crystal with gold-plated electrodes of manganese dioxide deposition kinetics and reaction mechanism of redox process. Measured by cyclic voltammetry in 0.1 MNa2SO4 δ-MnO2 oxidation of the solution pH decreased 3.95 pH gradually increased during the restore process, and finally returned to the initial value, indicating a reversible change with the electrode potential, MnO2 electrode surface occurs the embedding and extraction of hydrogen ions.

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