Metal-Organic Frameworks Derived Electrode Materials For Supercapacitor

Supercapacitor is a new type of energy storage device between traditional capacitors and batteries.Compared with batteries,supercapacitors generally have higher power density and longer cycle life.It has attracted wide research attention about how to develop excellent electrode materials due to its key role in the performance of supercapacitors.To date,the rational design and synthesis of novel metal organic frameworks?MOFs?have attracted intense attention because of their interesting topologies and extensive potential applications in many areas.The unique pore structure of MOFs molecules can provide suitable pores,allowing electrolyte ions to pass rapidly during charge and discharge.Therefore,MOFs materials have been widely used as supercapacitor electrode materials.Due to the presence of a large number of metal cations in the structure,MOFs can provide a high faraday capacitance.In addition,other metal ion sources or conductive substances can be introduced into the metal frame,so the MOF-based material is naturally suitable as sacrificial templates for materials with nanostructures,such as metal oxides,carbides and their composites.Therefore,MOF-derived materials have shown their potential applications in supercapacitor due to their generally porous structure and large specific surface area.In this thesis,a series of composites derived from MOFs were successfully synthesized for the first time and applied to the electrode materials for supercapacitor.The composites were examined by XRD measurement,raman measurement,TEM measurement,and so on.The electrochemical performance of materials were characterized by electrochemical station.The main results and innovations are as follows:?1?In second chapter,an effective strategy for homogeneous and polyporous WO₃@CuO composite has been reported by heating a POMs@MOFs template?POMs=polyoxometalates?,in which the W-POMs are incorporated into Cu-MOFs as secondary building units.The excellent doping of WO₃ to CuO contributes to the excellent electrochemical performance of the composite electrode,which exhibits a specific capacitance of 284 F g^-1 at a current density of 1 A g^-1,much higher than pure CuO electrode(48 F g^-1).Moreover,the composite material has shown longer cycle life of 85.2%capacitance retention over 1500 cycles.?2?In the third chapter,we successfully demonstrates a metal-organic framework xerogels?MOXs?derived strategy to prepare nanoporous carbon?NPC?with aluminum oxide?Al₂O₃?nanoparticles by the optimization of calcination temperature as highly active electrode materials for supercapacitors.The incorporation of CNTs into Al-MOX leads to an inherent improvement in surface area and an intrinsic increase in specific capacitance.The nanostructured Al₂O₃/C/CNTs hybrid shows high specific capacitance of 600 F g^-1at a current density of 1 A g^-1 and excellent capacitance retention up to 86%after 5000 cycles.?3?In the fourth chapter,a composite of nanoporous carbon/CNTs with unique structure has been prepared by pyrolysis of Al-MOXs/CNTs template.The composite carbon material has been used as supercapacitor electrode,and its electrochemical performance has been tested under three-electrode system.This unique structure ensures fast and efficient faradaic reaction in the electrode,resulting in excellent electrochemical performance,especially higher capacitance value than pure nanoporous carbon.