Preparation Of Co₃O₄ Composite Material By MPCVD Method And Study On Its Electrochemical Performance

With the development of human society,the energy crisis is becoming increasingly serious.Then people begin to focus on developing new energy storage devices.As a new type of energy device,supercapacitor has been widely used in power,transportation,industry and machinery and other fields because of its superior fast charging and discharging performance,good cycle stability,environmental protection and pollution-free characteristics.Electrode materials,as the core component of supercapacitors,have attracted great attention from scientists.In this project,microwave plasma chemical vapor deposition technology was used to fabricate composite electrode materials based on Co₃O₄ powder,and a variety of detection and analysis were conducted on the experimental results.The main conclusions are as follows:?1?Microwave plasma etching was used to process the porous Co₃O₄ spherical powder.The results showed that plasma etching can improve its electrochemical activity by creating abundant oxygen vacancies on the surface of the material and adjusting the valence state ratio of the elements.As an electroactive material,the powder has good pseudo capacitance properties.The specific capacitance gradually increases with the processing time and then becomes stable.After processing for a certain time,the specific capacitance of Co₃O₄ powder can reach 128 F·g^-1,which is2.4 times of that of raw materials.Moreover,it has good cycle stability and can maintain 96.3%initial capacitance after 4000 cycles.?2?A graphene shell with excellent electrical conductivity was coated on the surface of porous spherical Co₃O₄ powder by microwave plasma chemical vapor deposition.The valence ratio of atoms and oxygen vacancies are controlled by etching of active groups in microwave plasma.It is used to enhance the electrochemical properties of materials.The results showed that the graphene layer on the powder surface had the best quality when the ratio of Ar,H₂ and CH₄ in MPCVD was 9:10:1,and deposited for 10 min.Co₃O₄@Gr composites have typical pseudo capacitance characteristics,with a specific capacitance of 192.8 F·g^-1,and a capacitance retention rate of 98.5%after 20000 cycles with the current density of 10 A·g^-1.Therefore,MPCVD method was verified to be an effective method to improve the electrochemical properties of Co₃O₄ by coating graphene shell on the surface.?3?The precursor were coated on the surface of Co₃O₄ powder by the method of dissolution and mixing.And then MoS₂ nanosheets were synthesized on the surface of spherical Co₃O₄ powders by MPCVD.Finally the core-shell structure Co₃O₄@MoS₂composites with high electrochemical properties were prepared.Successful synthesis of MoS₂ on the surface of Co₃O₄ powders was confirmed by a series of analytical methods.And the surface morphology,composition structure and valence state of elements were analyzed.In addition,the performance of the composite material was tested by cyclic voltammetry and galvanostatic charge-discharge method.The results show that the synergistic effect of Co₃O₄ core and MoS₂ shell can effectively improve the electrochemical performance of the material.The specific capacitance of Co₃O₄@MoS₂ composite can reach 337 F·g^-1,and it has excellent rate performance and cycle stability.