Preparation And Electrochemical Perfoemance Of Ni-based MOFs And Their Oxides

In recent years,with the economic development and population growth,energy issues have become more and more important for human society.In a severe social situation,it is imperative to increase the energy conversion rate and utilization rate.Supercapacitors have attracted extensive attention due to their large power density,high cycling stability,and rapid charge and discharge characteristics.Metal oxides are considered to be one of the most promising materials because of their simple preparation process and low raw material costs.However,metal oxides undergo volume expansion during charging and discharging,resulting in the pulverization of active materials and a decrease in ion transmission rate.To solve this problem,a series of metal-organic framework materials and porous metal oxide materials werepreparedbysolvothermalmethodandannealingtreatment.The microstructure,surface morphology and electrochemical properties of the materials were systematically studied.The main research content is as follows:Using nickel foam as a nickel source and 2,5-dihydroxyterephthalic acid as a coordination agent,a metal organic framework?MOF?was grown on the nickel foam by solvothermal method and the electrochemical properties of its oxides were studied.the study.The specific capacitance of the Ni O electrode material is196.36 F·g^-1.After 5000 cycles of charge and discharge,the material retention rate of the material is 78.8%.Monodisperse MOF-74 was prepared by solvothermal method,and its microstructure,surface morphology and pore size structure were studied.The formation of monodispersed MOF-74 was investigated by controlling the concentration of reactants in the solvothermal method,the amount of surfactant added,and the ratio of the two inorganic metal salts added.Through a one-step annealing process,a metal oxide electrode material is prepared by subjecting a monodispersed MOF-74 material to high-temperature annealing.Although Ni O and Co₃O₄ have lower specific capacitance than Ni O and Co₃O₄,the Ni²⁺/Ni³⁺and Co²⁺/Co³⁺redox pairs of composite metal oxides can simultaneously undergo multiple electron reactions.Therefore,the materials have higher specific capacitance and cycle stability.Electrochemical test results show that the specific capacitance values of Ni O,Ni_1.71Co_1.29O₄,Ni Co O₂,Ni Co₂O₄,and Co₃O₄ in the 6 mol·L^-11 KOH electrolyte are 181.5 F·g^-1,247.3 F·g^-1,471.5 F·g^-1,684.0 F·g^-1,and 105.0 F·g^-1,respectively,after 3000 cycles of continuous charge and discharge,their capacitance retention rates It is 64.1%,82.5%,92.8%,85.43%,and 74%.The excellent specific capacitance and cycling stability mainly come from the rich pore structure of metal oxide materials prepared by this method.In this paper,through the design of mesoporous materials,several kinds of nickel-based composites prepared have excellent electrochemical performance and are expected to be used in electrode materials of future supercapacitors.