Electrospinning-Assisted Assemblies Of ZIFs Nanoparticles And Their Derived Materials For Electrochemical Performance

The preparation of one-dimensional(1D)nanofiber materials by electrospinning technology is one of the most important academic and technological activities in the material science and technology field in recent ten years,and it is also a powerful ways to assemble nanoparticles(NPs)and prepare functional materials.The composition and morphology of the electrospun nanofibers are also easily regulated,and the network structure of the nanofiber is beneficial to the mass transfer and so on.Electrospinning technology has become one of the main ways to effectively prepare nanofiber materials because of its advantages such as simple manufacturing facility,low spinning cost,wide variety of spinnable substances and controllable process.The electrospinning technology has been used to prepare various kinds of nanofibers,including organic,organic/inorganic composites and inorganic nanofibers.The nano materials and their derivatives are applied in biological,catalytic and new energy fields.Metal-organic frameworks have supramolecular structure.They are huge diversity constructed by metal-ions and organic ligands,and have unique porous structure of solid materials.Its porous structure,large specific surface area,structure and functional diversity,and many active sites enable them to be applied in many aspects,such as fuel electrode negative electrodes,lithium-ion batteries anode materials,photocatalytic hydrogen production,and degradation of organic matters.In recent years,the research mainly concentrated in the direct synthesis of MOFs nanoparticles dispersed,then direct carbonization and other way of doping.It was easy to cause the material of metal sintering in the carbonization.It was also rarely reported that the nanometer level MOFs as precursor were used to form 1D structure materials.This paper is mainly about the combination of electrospinning technology and MOFs.Then we can get different morphologies and metal contents of MOFs nanofibers by adjusting the morphology of 1D nanomaterials.By controlling the size and metal content of MOFs nanoparticles,we get 1D metal and heteroatom doped carbon nanofibers,and discuss their electrochemical properties.The research progess and achievements in this paper are as follows.1,Through the electrospinning technique successfully assembled ZIFs prepared for the first time the tunable MOFs nano fiber has a homogeneous 1D structure,the change of the proportion of Zn and Co in BMZIFs assembly of 1D nanomaterials(ES-BMZIFs),introducing inert gas high temperature carbonization can directly change to 1D porous carbon nanofibers.During the carbonization process,due to the blocking of polymer PAN,the sintering problem of Co NPs during carbonization was successfully solved,and the Co-Nx active sites formed uniformly distributed on the surface and inside of the material.This structure helps to make the derivative have the highest specific surface area,and the multistage channel,and can significantly exposure of the active site.As expected,the doped carbon nanofibers have excellent electrocatalytic properties,durability,and methanol resistance compared with the commercial 20%Pt/C catalysts under the same experimental conditions.The onset potential and half-wave potential of the doped carbon nanofibers are-0.08 V,-0.154 V in alkaline electrolyte and 0.52 V,0.43 V in acid electrolyte(vs Ag/AgCl),respectively.2,We successfully prepared the 1D porous Co3O4@ C nanofiber,and assembled ZIF-67 NPs by direct electrospinning.Then,it was subjected to reduction at high temperature and oxidation at low temperature.The two processes got the 1D metallic oxide nanofibers(ES-CNCo3O4).It should be emphasized that the Co3O4 nanoparticles made of carbon fiber in this work have hollow structure,which has been proved to have better electrochemical performance compared with solid nanoparticles.During the pyrolysis process,the cobalt monomer can catalyze the surrounding carbon graphitization simultaneously,making the derivative have a good affinity to the electrolyte.In addition,carbon coated four oxide three cobalt nanoparticles can also reduce the structural changes in the charge and discharge process,thus improving the stability of the composite.The 1D porous structure with large specific surface area is beneficial to the transport of lithium ions and electrolytes,especially the formation of micropores is beneficial to the exposure of active sites.These factors contribute to the improvement of the reversible capacity and cycle performance of ES-CNCo3O4.As expected,ES-CNCo3O4 as a negative electrode material of lithium-ion batteries,it has high specific capacity and energy output,at the same time,it also shows excellent cycle performance and rate performance.