With Different Morphologies Of Cobalt Oxide Capacitance Performance Study

In this paper,the preparation of Co₃O₄ with different shapes and sizes by solvothermal-thermal decomposition and solvothermal method were mainly reported.The formation mechanism of Co₃O₄ was investigated initially.The effects of morphology and size on their electrochemical performance were mainly investigated.The capacitive performance of Co₃O₄/MWCNTs composite electrode was also tested. The main contents are as follows:Co₃O₄ with hexagonal platelets was synthesized by solvothermal-thermal decomposition method.The structure and morphology of the precursor and product were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results showed that heat treatment temperature has great influence on the shape and size of the products.The shape and size of the precursor was maintained when treated at 200℃.Electrochemical properties of Co₃O₄ electrode were performed by cyclic voltammetry(CV),galvanostatic charge/discharge and altemating current(AC)impedance method.The results indicated that,in the potential range of -0.4～0.46 V(vs SCE),the Co₃O₄ obtained by 200℃showed excellent capacitive performance and charge/discharge ability at high current density in 2 mol·L^-1KOH electrolyte.The initial specific capacitance of single Co₃O₄ electrode reached 203.4 F·g^-1and 92%was maintained after 1000 cycles.Nanostructured Co₃O₄ with different morphologies were synthesized by solvothermal method using different cobalt salts in water and n-butanol solvent system with polyethylene glycol 20000 as dispersant. The structure and morphology of the precursors and products were characterized by IR,X-ray diffraction(XRD)and transmission electron microscopy(TEM).The results showed that the shape and size of Co₃O₄ can be controlled by altering the anions in the reaction system.The results of electrochemical tests indicated that the shape and size of Co₃O₄ had remarkable influence on its capacitive performance.In the potential range of -0.4～0.55 V(vs SCE),the spherical Co₃O₄ obtained from cobalt nitrate showed excellent capacitance performance in 2 mol·L^-1KOH electrolyte.The initial specific capacitance of single Co₃O₄ electrode reached 362.0 F·g^-1and 90%was maintained after 400 cycles.The capacitive performance of Co₃O₄/MWCNTs was investigated. The results showed that the addition of MWCNTs can improve the capacitive performance of Co₃O₄.The composite electrode showed excellent performance when the mass ratio of Co₃O₄ to MWCNTs is 90:10.The initial specific capacitance of single Co₃O₄ electrode reached 441.1 F·g^-1.