Nanoarrays Composites Generated From Cobalt-Metal Organic Framework And Their Electrochemical Storage Application

Metal-organic frameworks?MOFs?have tunable porous structures and nanochannels,which used as high-performance electrode materials for supercapacitors will accelerate ion transport during charging and discharging processes.Flexible supercapacitors meet the demand of wearable and portable electronic products because of their small size,portability,and ultra-thinness.In this paper,based on the structural advantages of MOF and the flexible characteristics of carbon cloth,cobalt compound nano-array electrodes with regular morphology was prepared by in-situ growth of cobalt-based MOFs?ZIF-67?on the surface of carbon cloth.Two schemes were designed and their electrochemical energy storage properties were systematically studied.The main contents of the thesis are as follows:In the first scheme,cobalt oxide?CoO?nanowires have been hydrothermally grown on the surface of carbon cloth.Then ZIF-67 has been grown in situ on the surface of nanowire.Finally,CC@CoO@S-Co₃O₄ core-sheath nanoarrays has been synthesized by hydrothermal method.The area specific capacitance of CC@CoO@S-Co₃O₄ in the three-electrode system can reach1013 mF cm^-2(1 mA cm^-2).When the current density expands to 20 mA cm^-2,the area specific capacitance can still be retained at 67.8%.The Flexible supercapacitor assembled with porous carbon derived from ZIF-67 exhibits good bending resistance with a volumetric specific capacitance of 1.99 F cm^-3 at 2 mA cm^-2.The energy density is 0.71 mWh cm^-3 at a power density of 21.3 mW cm^-3.The second scheme studies the electrochemical performance of nano-array through interface engineering.First,the surface of the carbon cloth has been pretreated with dopamine to obtain a hydrophilic carbon cloth.Then,ZIF-67 nanosheets have been grown in-situ on the surface thereof and calcined in nitrogen to prepare cross-linked Co₃O₄.Finally,chemical reduction has been carried out with sodium borohydride to obtain an oxygen vacancy Co₃O₄nanofilm.The flexible electrode has an area specific capacitance of 459.64 mF cm^-2 at the current density of 0.5 mA cm^-2 and the specific capacitance can remain about 73.9%after15,000 cycles at 2 mA cm^-2.In general,Co-MOF derived metal oxide electrodes grown in-situ on carbon cloth have regular array structure,excellent bending resistance and good electrochemical energy storage performance,which indicates that our schemes will promote the further development of high-performance flexible energy storage devices.