Preparation And Electrochemical Performance Of MOFs Decorated Electrospun Fibers

With the rapid development of society,nanotechnology plays an important role in this technology torrent,which is inseparable from the innovation of nanomaterials,and electrospinning technology plays a key role as an important method for preparing continuous nanofibers.The technology is economical and environmentally friendly,and the preparation is simple.Electrospun fibers are often combined with other functional materials to make them more widely used.At the same time,metal-organic framework materials have high specific surface area,high porosity,structural order and stability,but due to their size limitations,it is difficult to apply on a large scale.Therefore,we have used electrospun fibers as carriers,using electrostatic interaction to prepare electrospun fibers loaded with metal-organic framework materials,and obtaining porous carbon fiber composite materials by carbonization for use in supercapacitors and electrolyzed water fields.The main research contents and results are as follows:?1?Polyacrylic acid?PAA?and polyvinyl alcohol?PVA?solutions of the same mass ratio were electrospun for spinning solution to obtain PAA/PVA electrospun fibers.The Zn²⁺was adsorbed onto the surface of the electrospun fiber after cross-linking by electrostatic action,and the organic ligand was combined with Zn²⁺to prepare the PAA/PVA electrospun fiber loaded with ZIF-8.After carbonization at different temperatures,a ZIF-8-based porous carbon fiber composite material is obtained,which is used as a supercapacitor electrode material.Through the morphological and structural characterization,it is proved that ZIF-8has been successfully loaded onto the surface of PAA/PVA electrospun fiber.At the same time,the ZIF-8-based porous carbon fiber composite with a carbonization temperature of 900?has the largest specific surface area.Through electrochemical tests,it was found that the specific capacitance of ZIF-8-based porous carbon fiber composites with a carbonization temperature of 900?is higher than the specific capacitance of ZIF-8-based porous carbon fiber composites with carbonization temperatures of 800?and 1000?.When the current density is 1 A/g,the specific capacitance of the ZIF-8-based porous carbon fiber composite material having a carbonization temperature of 900?is 151 F/g.The material has good charge-discharge cycle stability.At a current density of 5 A/g,the specific capacitance still retains 98.9%of the initial specific capacitance after 10,000 cycles of charge and discharge.?2?Using the immersion method,the cross-linked PAA/PVA electrospun fiber membrane is immersed in a cobalt nitrate solution,Co²⁺is obtained on the surface of the electrospun fiber,and the electrospun fiber membrane is immersed in the organic ligand solution to realize ZIF-67.Assembly on the surface of PAA/PVA electrospun fibers.The ZIF-67-based porous carbon fiber composite material is obtained by treating at different carbonization temperatures,and is used as an electrocatalyst for oxygen evolution reaction and hydrogen evolution reaction.Through the morphology and structural characterization,it was found that ZIF-67 was loaded onto the surface of PAA/PVA electrospun fiber.The specific surface area of ZIF-67-based porous carbon fiber composite with carbonization temperature of 700?was larger than that of carbonization temperature of 600?,800?and900?.Electrochemical tests show that ZIF-67-based porous carbon fiber composites with a carbonization temperature of 700°C show better oxygen evolution performance.In a 0.1 M KOH solution,when the current density is 10 mA/cm²,the ZIF-67-based porous carbon fiber composite with a carbonization temperature of 700?has an overpotential of 0.33 V and a corresponding Tafel slope of 175.87 mV/dec;At the same time,ZIF-67-based porous carbon fiber composite with carbonization temperature of 700?showed good hydrogen evolution performance.ZIF-67-based porous carbon fiber composite with carbonization temperature of700?in current density of 10 mA/cm² in 0.5 M H₂SO₄ solution The material has an overpotential of 0.18 V and a corresponding Tafel slope of 63.65 mV/dec.In addition,the ZIF-67-based porous carbon fiber composite material having a carbonization temperature of700?exhibits good stability in both the oxygen evolution reaction and the hydrogen evolution reaction.?3?The ZIF-67-loaded PAA/PVA electrospun fiber was obtained by immersion method,and carbonized at 600?,700?and 800?,and then subjected to acid treatment to make pores,and a high specific surface area ZIF-67-based porous carbon fiber composite material was prepared.Used as a supercapacitor electrode material.Through the morphological and structural characterization,it is found that many pores appear on the surface of ZIF-67-based porous carbon fiber composites,which have a high specific surface area,and the ZIF-67-based porous carbon fiber composite with a carbonization temperature of 700?has the largest specific surface area.Electrochemical tests show that the ZIF-67-based porous carbon fiber composite with a carbonization temperature of 700?has a higher specific capacitance.In a 2.0 M H₂SO₄ solution,when the current density is 1 A/g,the ZIF-67 has a carbonization temperature of 700?.The specific capacity of the porous carbon fiber composite material was 95.44 F/g.At the same time,the material has good charge-discharge cycle stability.At a current density of 5 A/g,the constant current charge and discharge is10,000 times,and the specific capacitance loss of the ZIF-67-based porous carbon fiber composite material with a carbonization temperature of 700? is 0.8%.