Preparation And Electrochemical Properties Of ZIF-67 Derived Metal (Hydrogen) Oxide Composites

With the consumption of fossil energy,it is of great practical significance to develop nano-electrode materials with outstanding electrochemical performance to achieve high-efficiency energy conversion and storage.The metal?hydrogen?oxide electrode material has a high theoretical specific capacity,however,the poor conductivity of Co₃O₄ affects its electrochemical performance and cycle life.Metal organic framework compounds?MOF?have the advantages of species diversity,tunable pore size and high specific surface area.The use of MOF materials and their derivatives in high performance electrochemical energy storage electrode materials has become a hot topic.In this paper,in order to improve the electrochemical performance of MOF material and realize its application in the field of electrochemical energy storage,the transition metal?hydrogen?oxides with unique structure and high specific surface area were synthesized using ZIF-67?Zeolitic Imidazolate Frameworks?and nano-materials compounded with carbon materials as self-sacrificing templates.The main work of this paper is as follows:?1?ZIF-67 was successfully loaded onto graphene oxide?GO?sheet by room temperature stirring method to prepare ZIF-67/GO precursor template material.Porous Co₃O₄/rGO nanomaterials derived from ZIF-67 were obtained after calcination.The results show that its specific capacity is 238 F.g^-1 at 1.0 A.g^-1 current density,which is much higher than that of polyhedral Co₃O₄(157 F.g^-1)induced by ZIF-67 alone.When constant current charging and discharging is carried out at current density of 8 A.g^-1,the cycle stability is very strong;?2?Firstly,ZIF-67 grains were compounded with acidified multi-walled carbon nanotubes?MWCNTs?to form a"beaded"interpenetrating structure.Using ZIF-67/MWCNTs as the precursor template,the Co₃O₄/MWCNTs were prepared by calcination at high temperature.In addition,ZIF-67/MWCNTs were dissolved in the ethanol solution of Ni?NO₃?₂ to prepare Co-Ni LDH/MWCNTs by acid etching.The results show that the specific capacitance of Co₃O₄/MWCNTs and Co-Ni LDH/MWCNTs is 222 F.g^-1 and 778 F.g^-1 at 1 A.g^-1 current density respectively,and the specific capacity of Co₃O₄/MWCNTs is 62.1%at high current discharge density of20 A.g^-1,showing excellent rate performance;?3?Flower-like and hollow Co-Ni LDH?Layered Double Hydroxide?were synthesized by acid etching with ZIF-67 crystal as template and cobalt source when Ni?NO₃?₂ was added.The results show that the flower-like Co-Ni LDH consists of large and ultra-thin nanosheets has a large specific surface area(115.3 m^2.g^-1).The specific capacitance of 1480 F.g^-1(1.0 A.g^-1)in 6 M KOH electrolyte is better than that of the hollow structure Co-Ni LDH(1280 F.g^-1).At high current density(10 A.g^-1),the specific capacitance keeps 66.1%,which has good rate performance.