Study On Preparation Of Carbon@Metal Oxide Composite Materials And Their Electrochemical Properties

The aim of this research is to explore the use of cheap raw materials and simple synthetic techniques for preparing high specific capacitance of mesoporous carbon materials, metal oxide materials and mesoporous carbon@metal oxide composite materials which were used as the electrode materials of super-capacitors. The as-prepared materials were analyzed and characterized for its structure and performance. The major contents can be summarized as follows:(1) In this paper, worm-like mesoporous carbon was synthesized with metal-organic coordination polymers (MOCP) as the carbon precursor, glycerol as additive, and directly calcined under a high temperature. The synthsied products have a bimodal pore size distribution. The effect of the pore structure and crystal structure on changing with the different polymer precursor and the additive was characterized by X-ray diffraction analyzer and specific surface area analyzer. The electrochemical performance of the worm-like mesoporous carbon was characterized by cyclic voltammetry, galvanostatic charge/discharge curves and electrochemical impedance spectroscopy. The experimental results show which the specific surface area of mesoporous carbon materials can effectively improved and the largest surface area up to 2857m2/g when the appropriate amount of bismuth nitrate was added into the carbon precursor. The pore size distribution of the mesoporous carbon mostly focused on 2.6nm and 6.3nm. The specific capacitance of the materials testing under the current density of 50mA/g in 6mol/L KOH aqueous solution is up to 344F g-1.(2) Bi2O3 electrode materials were synthesized by hydrothermal synthesis method using bismuth nitrate solution as the raw material, NaOH solution as the mineralization agent and polyethylene glycol (PEG-400) as the surfactant. The structure, the morphology and the electrochemical performance of the Bi2O3 electrode materials were further studied. The experimental results illuminate that the Bi2O3 material synthesized by hydrothermal method has a rod-like morphology by SEM and a pure a-phase by XRD diffraction. The a-Bi2O3 electrode material has a very excellent supercapacitance performance and high current charge/discharge performance by cyclic voltammetry, galvanostatic charge/discharge and cycle life test. Under the current density of 100mA/g, the specific capacitance is up to 1333F/g, even with 5A/g discharge current conditions for 600 cycles, the specific capacitance is still retained 720F/g.(3) The worm-like mesoporous carbon materials were employed as the support, subsequantly, dipped the different concentrations of bismuth nitrate solution and manganese nitrate solution for absorbing Bi3+ and Mn2+, respectively. The microwave synthesis method was adopted to synthesize mesoporous carbon/Bi2O3 and mesoporous carbon/Mn3O4 composite electrode materials. The structure and morphology of these composite materials were analyzed and characterized and the electrochemical performance was researched in detail. The results show that Bi2O3 and Mn3O4 nanoparticles were formed and supported on mesoporous carbon quickly. The particle size of Bi2O3 and Mn3O4 was ranged from 30 to 200nm. In the process of charge/discharge, the Bi2O3 and Mn3O4 particles provide pseudo-capacitance via a redox reaction and mesoporous carbon contpobutes double-layed capacitance. Thus, the composite materials significantly increase the capacitance performance.