Synthesis Of Co₃O₄/GNP Composite And Its Electrochemical Properties

Supercapacitor has attracted more and more attention because the advantages of the high power density(as high as 10 kw·kg^-1),long cycle life?as high as 100 thousand times?and short charge and discharge time.The performance of supercapacitor is directly determined by its electrode material,which induced that development of electrode material with large specific capacitance,good stability,good cycle performance and low price becomes the most important task.Researches of the cobalt tetroxide/graphene composites as supercapacitor's electrode materials have become a research focus.Agglomeration was effectively prevented,and the large surface area and good electrical conductivity of graphene ensure enhanced contact between composites and electrolyte solution.Cycle performance of the composite has been improved.However,most of the researches on Co₃O₄/graphene nanocomposites contain two steps.Firstly,cobalt oxide precursor/graphene oxide composites was synthesized.Secondly,the above composites was heat treated and Co₃O₄/graphene nanocomposites was achieved.Here,Co₃O₄ nanoparticles and Co₃O₄/GNP composites were successfully prepared by one-step in-situ hydrothermal method.The crystal structure and morphology were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Raman spectrum?Raman?.The effects of Co₃O₄ morphology and Co₃O₄/GNP ratio on the electrochemical properties were investigated via three-electrode method.The following results were obtained.1.GNP was achieved by mechanical stripping method,and the lamellar thickness of GNP is about 4 nm,with smooth surface,and low defect density.2.Co₃O₄ nanoparticles and Co₃O₄/GNP nanocomposites were prepared by one-step in-situ hydrothermal method and the electrochemical properties of Co₃O₄/GNP nanocomposite was more excellent than Co₃O₄ nanoparticles.The might reason is that Co₃O₄ nanoparticles were uniformly dispersed on the GNP layer.The specific capacitance of Co₃O₄/GNP nanocomposite reached 355 F·g^-1 and internal resistance was about 0.88 ?.3.Spherical,cube and rodlike Co₃O₄ nanoparticles were successfully synthesized using water and n-butanol as mixed solvents.With the ratio increase of n-butanol of solvent.the morphology of particle changed from spherical to cube and rodlike,and the cubic Co₃O₄ nanoparticles had better electrochemical performance,with specific capacitance of 509 F·g^-1 and internal resistance of 2.10 ?.4.The spherical Co₃O₄/GNP nanocomposite?S-Co GNP?and cubic Co₃O₄/GNP nanocomposite?C-Co GNP?were preparated by one step method,and the effects of Co₃O₄ morphology and the mass ratio of Co₃O₄ and GNP on electrochemical properties.The results showed that S-Co GNP composite with the ratio of 3:1 had excellent electrochemical performance,the specific capacitance was 355 F·g^-1 and the resistance was 0.88 ?.C-Co GNP composite with the ratio of 8:1 had excellent electrochemical performance,and the specific capacitance reached 542 F·g^-1 and the resistance was 1.57 ?.