Synthesis And Property Of Manganese Oxide And Nanocomposite

Electrochemical capacitors (ECs) are energy-storage devices with specific energy higher than conventional dielectric capacitors but lower than batteries, which their specific power capabilities are higher than batteries but lower than conventional dielectric capacitors. ECs could also be used as electric components, power sources for small apparatus and direct current switches. ECs are based either on the electrical double layer capacitance of electrode materials with high surface area such as activated carbon(AC), or on the pseudocapacitances of redox reactions of metal oxides and conducting polymers, as well as the combination of these two. Many researchers pay more attention to the metal oxides in order to get higher capacity.Different manganese oxides were prepared by hydrothermal and chem-mixed precipitation method, respectively. Several techniques such as XRD, SEM, TEM, BET, TG-DTG, cyclic voltammetry(CV) were used to study the physical and chemical properties and electrochemical performances of the synthesized materials.MnO2/13X molecular sieve composites were synthesized by a chem-mixed precipitation method. X-ray diffraction(XRD) showed that the as-prepared sample was amphorous. The supercapacitive property of the as-prepared composite was investigated by cyclic voltammetry and galvanostatic charge-discharge techniques in 1 mol·L-1KOH electrolyte, with potential scope of-0.1V～0.58V. The results showed MnO2/13X molecular sieve composites with 30% mass fraction of manganese oxide exhibited good electrochemical characteristics. The specific capacitance of the MnO2/13X composite is 134 F·g-1 at 100 mA·g-1 current density.Mesoporous manganese oxides were successfully prepared via a simple hydrothermal method using three kinds of surfactants dodecyltrimethylammonium bromide(DTAB), cetyltrimethylammonium bromide(CTAB) and octadecyltrimethylammonium bromide(OTAB) as structure directing agents. The synthesized samples were characterized by the X-ray diffraction(XRD), Brunauer-Emmett-Teller(BET), scanning electron microscope(SEM) respectively. The supercapacitor property of the as-prepared composite was investigated by cyclic voltammetry in 1 mol·L-1Na2SO4 electrolyte. The experimental results show that there are influences of carbon-chain length of surfactants on not only crystal structure and metal valence of the products, but also specific surface area and pore size of the prepared materials. The specific surface areas are 60m2·g-1,25m2·g-1,7m2·g-1, and the pore sizes are 4nm,7nm,13nm for the mesoporous materials prepared using structure directing agents DTAB,CTAB,and OTAB,respectively. The prepared material can be used for the electrodes for electrochemical supercapacitors.