The Synthesis Of Porous Carbon And Its Composites Derived From MOFs And Their Application For The Supercapacitor

With the rapid development of human social civilization,energy problems are gradually upgrading.New energy development and energy storage problems become a top priority,in which the storage of electricity is particularly important.As a new type of energy storage components,supercapacitor is widely used in civil and military fields with the preparation of low cost,quick speed of charge and discharge,strong transferring ability of electric charge,safety and environmental protection and so on.According to super capacitor energy storage principle,super capacitors can be divided into two layers of electric capacitors and pseudo-capacitance,Electrode material performance is the key to the preparation of high performance supercapacitors?Because the electric double layer capacitor is through its double electric layer structure charge storage,So the large specific surface area of its electrochemical performance is of great significance;The pseudo-capacitance is mainly carried out by its internal reversible redox reaction for charge storage,It is desirable that the electrode material contains a substance which can undergo a reversible redox reaction the larger the specific surface area of the supercapacitor electrode material,the better the electrochemical performance is.In addition to that,good rate performance,recycle stability and good conductivity are also the key to super capacitor performance.Since carbon material can be prepared with a large specific surface area,but poor conductivity,therefore,the carbon matereials with both large surface area and high conductivity is demanded for use as the electrode material and super capacitor.But in practical applications,the carbon material is still difficult to meet the demand.Graphene as a new material,has excellent electrical conductivity and large specific surface area,is considered the ideal super capacitor electrode material.Metal-organic frameworks?MOFs?are crystalline materials with ultra-high porosity and large specific surface area.They are rich in micro/mesoporous structures and can be used as a precursor for the preparation of rich micro/mesoporous carbon materials.Based on the above consideration,We chose MIL-53?Al?and MIL-88?Fe?two MOFs structure,as a precursor,the porous carbon materials with rich pore structure and the composites of Fe₂O₃/porous carbon were prepared by means of calcination,pickling and activation,electrode materials for supercapacitors,showing a good performance of the electrochemical energy storage;The composite of MIL-53?Al?/reduced graphene graphene was prepared by in-situ preparation method using graphene oxide as precursors,electrode materials for supercapacitors,showing a good performance of the electrochemical energy storage.In this dessertation,we have done the work as follow:1.MOF-type based on MIL-53 was used as a precursor for preparation of hierarchical porous carbon materials,which has a specific surface area of 963 m²g^-1with the mesopore volume of0.05 cm³g^-1.The electrochemical performance of the supercapacitor was tested under alkaline electrolyte when the current density is 50 mA/g,the specific capacitance is 180 F/g.2.HPC/G obtained from MIL-53?Al?/GO composite with hierarchical porosity was synthesized by adjusting the feed ratio of MIL-53 and GO.The optimum feed ratio of the composite is 0.3wt%,and the MIL-53?Al?/GO composite has a surface area up to 1560m²/g.By calcinations of MIL-53?Al?/GO composite,the hierarchical HPC/G composite with surface area up to 1268 m²g^-1 and a better electrical conductivity was obtained.The study of the effect of carbonization temperature on the porosity and electrochemical properties of the supercapacitor electrode material were carried out.A HPC/G composite with its specific capacitance of 247 F/g in alkaline electrolyte under the current density of 50mA/g was gained.3.Use MIL-88?Fe?as precursor,use one-step calcination,a series of C/Fe₂O₃ composites were obtained at different temperatures in nitrogen atmosphere,And prepared as an electrode sheet,test it's electrochemical performance,Found in the alkaline electrolyte than the maximum capacitance of only 107 F/g,after analysis,It was found that the pore structure of the precursor had a significant effect on the electrochemical properties of the carbon-based composites,precursor with multi-stage pore structure is the best choice.