Preparation And Electrochemical Properties Of Carbon-based Cu-MOFs Composites

Replacing traditional energy with new energy is an important measure to promote the transformation of my country’s energy industry and achieve"carbon neutrality"and"carbon peaking"as soon as possible.Supercapacitors are a new type of electrochemical energy storage device commonly used for electrical energy storage and energy conversion.Carbon materials,as the only commercialized supercapacitor electrode materials,mainly rely on electrostatic action for energy storage,but their energy density is low and limited by the interface of the electric double layer,resulting in unsatisfactory capacitive performance.Metal-based MOFs have a unique three-dimensional nanoporous structure with high theoretical specific capacity,but their electrical conductivity and cycle life are poor.Therefore,in this paper,copper-based MOFs material is selected as the support layer,and nano-carbon material is deposited on its interface as the independent electrode of the supercapacitor.The phase,structure and electrochemical properties of the electrode materials were characterized by X-ray diffraction test,infrared spectrum test,scanning electron microscope test,transmission electron microscope test and comprehensive electrochemical test technology.The main research work is as follows:（1）To explore the effect of different reaction conditions on Cu-MOFs:copper acetate was used as the copper source,and the molar ratio of copper acetate to trimesic acid was 4:1,and the powders were prepared under different solvothermal temperature and time conditions.Cu-MOFs material.According to the SEM image,at 120°C for 12 h,the material has a clear structure and a regular three-dimensional structure,and the specific capacitance is 358 F/g at a scan rate of 10 m V/s in 6 mol/L KOH_aq.solution.（2）To explore the effect of oxidation temperature on the electrochemical properties of Cu-MOFs:The Cu-MOFs were subjected to high-temperature oxidation treatment at different temperatures for 9 h.The results showed that when the oxidation temperature was 300°C,the framework structure of Cu-MOFs destroyed.When the oxidation temperature is 200°C,the specific capacitance is enhanced to 398.8 F/g,the redox peak on the cyclic voltammetry curve is enhanced,and the pseudocapacitive performance is improved.（3）To explore the effect of different ratios of active components on the electrochemical properties of composites:Cu-MOF-NCS composite electrode materials were prepared by in-situ composite of Cu-MOFs with different ratios and nanoporous carbon spheres（NCS）.SEM image analysis shows that NCS is dispersed in the pores of the Cu-MOFs framework structure.When the addition of NCS is 2%of the mass of the copper source,NCS enhances the Faradaic process of Cu-MOFs and achieves a specific capacitance of 588.1 F/g at a scan speed of 10m V/s;When the amount is 5%of the mass of the copper source,the charge transfer rate is higher and the charge diffusion resistance is smaller than that of NCS.This is attributed to the porous structure of Cu-MOFs,which is favorable for the dispersion of carbon spheres,which makes the carbon spheres fully contact with the electrolyte.Cu-MOF-5%NCS@Ni electrode symmetric supercapacitor in 6 mol/L KOH_aq solution,the current density is 20 m A/g,and the specific capacitance retention rate is 96.7%after 800charge-discharge cycles.