Synthesis Of Fe-Metal-Organic Frameworks Derived Composites And Their Application In Supercapacitor

In order to solve the urgent global problem in the wide use of fossil fuels and consequent lack of fuel and environmental pollution,the development of various energy storage and conversion systems has been the subject of recent attention.The advantages of high power density,high efficiency and long life expectancy has made electrochemical supercapacitors one of the major emerging devices for energy and power supply.The properties of the supercapacitor are closed related with the electrode material,so it is indispensable to develop an high-performance electrode material with high power density and also high energy density.Metal-organic framework materials is a kind of periodic reticulate skeleton structure which is formed of oxygen or nitrogen organic ligand and transition metal connections.Because of its metal clusters and large surface area,it becomes a potential material for both electric double layer capacitor and faraday capacitance,which causes widespread attention.Recently,the newly emerging metal organic framework materials act as templates and/or precursors to fabricate porous carbons and related nanostructured functional materials based on their high surface areas,controllable structure and abundant metal/organic species in their scaffolds.In the present work,two metal organic framework materials(Fe-MIL-88?Fe-MIL-53)are synthesized firstly,and then used as precursors and templates to obtain the MOFs/RGO composites and FeOx@C composites for supercapacitors,respectively.The phase and morphology of as-obtained samples are characterized by XRD,SEM,TG and electrochemical properties are measured by cyclic voltammetry(CV),galvanostatic charge-discharge(GCD),electrochemical impedance spectroscopy(EIS).The main results are as follows:1.The Fe-MOFs/RGO composites were obtained in one step by FeCl3·6H2O as iron source,terephthalic acid as ligand with different concentrations of GO.The results showed that the addition of GO didn't inhibit the formation of crystals of MOFs,and the MOF crystals are well combined with graphene layers in good uniform distribution.Furthermore,the presence of GO improves the conductivity of the material significantly,and leading to the large specific capacitance and high rate capability.The specific capacitance of as-prepared Fe-MIL-88/RGO composite is 187.5 F/g at the scan rate of 10mV/s,while the specific capacitance of as-prepared Fe-MIL-88 is only 40.24 F/g at the same rate.The specific capacitance of as-prepared Fe-MIL-53/RGO composite is 156.7 F/g at the scan rate of 10mV/s,while the specific capacitance of as-prepared Fe-MIL-53 is only 85 F/g at the same scan rate;2.The FeOx@C composites were prepared via solid state conversion process of freshly prepared Fe-base MIL-88 and MIL-53crystal.The results demonstrated that as made FeOx@C composites displays well crystal and can be applied as a supercapacitor electrode and it energy storage performance were investigated in 1M KOH electrolyte.The results showed that the different phase components of the as-obtained product at the different carbonization temperature;The good electrochemical properties was achieved at the carbonization temperature of 900?.The specific capacitance of Fe-MIL-88 derived FeOx@C composites can reach 271.5 F/g at the scan rate of 10mV/s,while the specific capacitance of Fe-MIL-53derived FeOx@C composites is 191.2 F/g.The two-electrode configurations were also used to evaluate the capacitive performance of the electrode materials.It shows that the two-electrode cell exhibit good cycle stability,as a result,the materials has great potential in supercapacitor applications.