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Preparation and Capacitance Properties of Nanostructured Manganese Dioxide

Author: YangYuJuan
Tutor: HuangChengDe
School: Tianjin University
Course: Applied Chemistry
Keywords: Manganese dioxide Capacitance Performance Sol-gel method Hydrothermal Synthesis Nanorods Nanosheets
CLC: O614.711
Type: Master's thesis
Year: 2007
Downloads: 629
Quote: 3
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Abstract


Manganese dioxide as the conventional electrode active material applications is quite extensive. Nano-manganese dioxide materials with special physical and chemical properties, and thus its superior electrochemical performance. The supercapacitor has broad application prospects of new energy storage device, its electrode active material is currently one of the hot. This paper studies the preparation of nano-manganese dioxide material and capacitor performance. The sol-gel method, hydrothermal method, and a liquid phase method at room temperature were prepared the different manganese dioxide nanomaterials, and by X-ray diffraction analysis (XRD), transmission electron microscopy analysis (TEM), specific surface area (BET) , cyclic voltammetry (CV) and constant current charge and discharge test characterization techniques of the prepared sample physical and chemical properties and electrochemical properties were systematically studied. Citrate sol-gel synthesis, the citric acid and manganese acetate molar ratio of 0.5:1, does not add potassium nitrate, the pH value of the reaction system of 6,300 ° C calcined dry gel, and the manganese oxide obtained was acidified with dilute sulfuric acid processing, the final product to have a certain degree of agglomeration of the manganese dioxide nanofibers. Samples in 0.5 mo1 · L -1 Na2SO 4 solution, -0.15 0 .85 V (vs. SCE) potential range 66.5 mA · g -1 constant current charge and discharge, the discharge capacity of 133.58 F · g -1 . Hydrothermal synthesis of KMnO 4 and MnSO , 4 after the reaction at a lower molar ratio of the tunnel structure of α-MnO 2 ; than The main product of the high molar ratio for the layered structure of δ-MnO 2 , the latter of the layered structure is more conducive to intercalation and deintercalation of the H or Na, and therefore the better performance of its capacitance. Of KMnO 4 and MnSO 4 in the initial molar ratio of 1:1, 120 ° C hydrothermal reaction 6h diameter about 20 3 0nm, the so long 1μm uniform α-MnO 2 nanorods. KMnO 4 and MnSO 4 molar ratio of 3:1,120 ° C hydrothermal reaction at 2h, the flower-like sheet of the resulting sample for the nanometer scale, it belongs to the layered structure of the δ -MnO 2 . The crystallinity is poor, with an average particle size of about 8.3nm, 0.5 mo1 · L -1 Na2SO 4 solution, -0.2 1 .0 V (vs. SCE) potential range of 70mA · g -1 constant current charge-discharge measured obtaining the specific capacity of 259.19 F · g -1 . Molar ratio of 4:1 the KMnO 4 and MnSO 4 amorphous room temperature liquid phase reaction system δ-MnO 2 materials. 0.5 mo1 · L -1 Na2SO 4 solution in the potential range from -0.2 1 .0 V (vs. SCE), 94mA · g -1 constant current charge and discharge than the capacity of the manganese dioxide material up to 290.03 F g -1 ; 1880mA · g -1 constant current charge and discharge specific capacity is still 195.49 F g -1 . Constant current charge-discharge cycle life test (375mA · g -1 of the test), the first discharge capacity maximum to $ 227.84 F g -1 100 cycles after than the capacity of 200.12 F · g -1 , about starting than 88% of the capacity.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > The Ⅶ group metal elements and their compounds > The manganese Vice Family ( VII B group metal elements) > Manganese Mn
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