Preparation And Electrochemical Properties Of ZIFs Derived Ni-Co Oxide Nanocomposites

Metal Organic Frameworks（MOFs）is a new type of porous material,which combines metal center ions with organic ligands through coordination bonds,and then gets a highly ordered three-dimensional network structure through self-assembly.Structure and morphology of nanomaterials have an important influence on electrochemical properties.Through reasonable design of metal center ions and organic ligands,accurate control of reaction conditions and subsequent heat treatment steps,MOFs can be used as an excellent precursor template to synthesize MOFs-derived nanomaterials with ideal composition structure and properties.MOFs-derived nanomaterials normally have the advantages of tunable pore sizes,large number of active sites,and fast electron transport channels.However,it is still difficult to control the structure of MOFs-derived metal oxides at present.Moreover,MOFs-derived metal oxides possess weak electron transport capability,and the mechanism of morphological transformation during the pyrolysis process of MOFs-derived metal oxides is still unclear.Therefore,it is necessary to conduct in-depth studies on the structure and morphology control of MOFs-derived nanomaterials,the design of composite nanomaterials with conductive matrix or carbon materials,the mechanism of morphology transformation during the pyrolysis process,and the applications in the field of electrochemistry.In this paper,Zeolitic Imidazolate Frameworks（ZIFs）-derived nanomaterials with low-dimensional and three-dimensional structures were prepared.Their excellent electrochemical performance can be geiven by:changing the morphology of nanomaterials to increase their specific surface area,making the materials fully contact with electrolyte to increase ion osmosis,and compounding with carbon materials and ZnO to increase their electron transfer rate.The main research contents are as follows:Using ZIF-67 as template,Co₃O₄/NiCo₂O₄ double-shelled nanocages（DSNCs）were prepared and combined with rGO reduced graphene oxides（rGO）by adsorption to obtain Co₃O₄/NiCo₂O₄ DSNCs@rGO.It is found that the introduction of rGO in alkaline electrolyte has a great influence on its electrochemical Glu sensing performance.The enhancement mechanism of glucose（Glu）sensor performance and the synergistic effect between Co₃O₄/NiCo₂O₄ DSNCs and rGO was analyzed.ZnO/Co₃O₄/NiCo₂O₄/Ni foam nanocomposite materials were prepared using nickel foam,and have good performance in H₂O₂ detection.ZnO Nanowires（NWs）grown on the nickel foam can improve its surface roughness and increase the load of Co₃O₄/NiCo₂O₄ DSNCs;In addition,Co₃O₄/NiCo₂O₄ DSNCs can be dispersed well for full contact with electrolyte;Providing a fast electron transfer path between Co₃O₄/NiCo₂O₄ DSNCs and nickel foam,which accelerates the electron transfer rate.Without binder,the active sites of electrode material can be fully exposed to electrolyte.Phosphate buffer（PBS）with neutral p H was used to detect the electrolyte of H₂O₂,which is environmentally friendly.Ni_xCo_3-xO₄/CNTs（Carbon Nanotubes）nanocomposites were prepared through composition of CNTs with Ni-Co bimetallic oxide,in which porous Ni_xCo_3-xO₄ was evenly distributed on the surface of CNTs.Results showed that the materials own the best electrochemical performance when the mass ratio of Ni-Co is 1:1 and the reaction time was 2h,and the introduction of CNTs could improve their electrochemical performance.The preparation process is carried out at room temperature with a simple experimental conditions and a short reaction time.The Ni_xCo_3-xO₄/CNTs electrodes combined the rapid electron transfer characteristics of CNTs one-dimensional structure with the rich active sites of Ni_xCo_3-xO₄ to improve the battery-supercapacitor hybrid devices（BSH）properties of nanocomposites,and thereby extending the preparation of one-dimensional bimetallic oxide nanocomposites using ZIF-67 as template for alkaline BSH.The optimization of Ni_xCo_3-xO₄/Ni foam were studied,and highly optimied Ni_xCo_3-xO₄ on Ni foam was successfully synthesized with rGO.It was found that Ni_xCo_3-xO₄ with two-dimensional nanosheet structure could be obtained by using water as solvent.The introduction of nickel ions has a great influence on the morphology and electrochemical properties of the materials.The Ni_xCo_3-xO₄ nanosheets based on Co-ZIF provide sufficient electrode-electrolyte contact area for the porous network structure and ensure abundant reaction sites.rGO provides a convenient conductive network for electron transfer,and the synergistic effect between metal oxide and carbon materials helps to improve energy storage.Ni_xCo_3-xO₄ nanotubes arrays hierarchical structure（NAHS）/Ni foam nanocomposite materials with hierarchical structure were constructed.The effect of different reactants on the morphology of ZnO nano rod arrays（NRAs）was studied.2-methylimidazole（2-MIM）plays a key role during the synthesis of Ni_xCo_3-xO₄ NAHS.The Ni-Co mass ratio of Ni_xCo_3-xO₄NAHS/Ni foam was optimized by electrochemical performance analysis.Ni_xCo_3-xO₄ nanotube arrays with one-dimensional hollow structure provide a fast electron transfer pathway.The dense and uniform Ni_xCo_3-xO₄ nanosheets have two-dimensional cross-linking structure,providing a larger surface area and more active sites,thereby ensuring adequate contact area with the electrolyte.The special structure composed of one-dimensional,two-dimensional and three-dimensional multi-stage structure not only provides an effective ion transfer pathway,but also improves the surface area,so that BSH has excellent electrochemical properties.