Preparation And Electrosorption Properties Of Metal-organic Framework/Graphene Composites

Metal-organic frame（MOF）materials are characterized by well-developed pores,large surface area,adjustable function and structure,and electric charge on the surface.It is very suitable to be used as electrode material of supercapacitor and electrosorption desalting device.However,metal-organic framework materials have problems such as poor electrical conductivity and poor stability when used as electrode materials.Graphene has good electrical conductivity and porous structure.Combining graphene with MOF materials can improve its electron conduction ability and cyclic stability.Therefore,MOF/graphene composites have broad development prospects.In this paper,Ni-Co organic framework/rGO composite（NiCo-MOF/rGO）and Al organic framework/rGO composite（MOF-303/rGO）were prepared.And then investigated their electrochemical properties and electrosorption desalting performance.The main studies are as follows:1.NiCo_x-MOF complexes were prepared by the solvothermal method.And it was found that the electrochemical performance was best when the ratio of Niand Co elements was 1:1.When the scanning rate was 1 m V s^-1,the specific capacitance of the material could reach 920.6 F g^-1.NiCo-MOF/rGO was prepared by combining the MOF material prepared at a ratio of 1:1 with rGO to further improve the material’s magnification and charge conductivity.The electrode material has very good magnification performance,with a specific capacitance of 1229.1 F g^-1 at the scan rate of 1 m V s^-1 and 721.2F g^-1 at the scan rate of 20 m V s^-1.Moreover,its electrical conductivity was also improved,with a charge transfer resistance of 0.9Ω,due to the recombination of rGO.The electrosorption desalting test of NiCo-MOF/rGO composite showed that the electrosorption capacity of NiCo-MOF/rGO composite was 48.3 mg g^-1,respectively,when the applied voltage was 1.2 V,the flow rate was 20 m L min^-1,and the initial NaCl concentration was 800 mg L^-1.The cyclic adsorption-desorption experiments showed that it can maintain stable electrosorption performance.2.MOF-303 and MOF-303/rGO composites were prepared by hydrothermal reaction.When the scanning rate was 1 m V s^-1,the specific capacitance of the composite material was 747.1 F g^-1,which was much higher than that of the pure MOF material(427.21 F g^-1).The electrochemical impedance analysis of the composite showed that the charge transfer resistance was 1.2Ω.The MOF-303/rGO composite was tested for its electrosorption desalination capacity,which was able to reach 57.92 mg g^-1 under the conditions of voltage 1.2V,flow rate of 20 m L min^-1 and initial NaCl concentration of 800mg L^-1.And when the initial concentration was 1600 mg L^-1,it can achieved 4.2mg g^-1s^-1 ion removal rate.After multiple cycles of adsorption-desorption,the electrosorption capacity did not decrease significantly,showing a better cycle life.