In Situ Growth Of Nickle-based MOF Array Materials On Carbon Cloth And Their Electrochemical Performance

As a new type of green energy storage device,supercapacitor has attracted much attention because of its characteristics of fast charging and discharging,high power density and long cycle stability,etc.The key to its performance lies in electrode materials.Therefore,the development of advanced electrode materials with excellent performance has become a hot and difficult research area.As an emerging porous crystalline material,metal organic framework material（MOF）is regarded as a potential electrode material for supercapacitor because of its simple synthesis method,controllable structure and large specific surface area.However,the disadvantages of MOF materials in terms of their own poor conductivity and unstable structure lead to poor multiplicative performance and cycling stability,which limit their application in supercapacitor electrode materials.To address the above issues,in this paper,Ni/Co-MOF@CC composites were obtained by using active carbon cloth（CC）as the conductive substrate material,growing Ni-MOF arrays in situ on its surface by hydrothermal method and modulating its structure and composition by double ligand and doping with Co²⁺.This method of growing the active material in situ directly on the surface of carbon cloth without binder,while taking advantage of the excellent electrical conductivity,flexibility and double-layer energy storage the carbon cloth,to obtain high-performance composite electrode materials.Details of the research are as follows:1.The Ni-MOF@CC composites were prepared by in situ growth of monoligand Ni-MOF and dual-ligand Ni-MOF arrays on the surface of CC as a conductive substrate by hydrothermal method.The SEM test results showed that:the Ni-MOF synthesized by dimethylimidazole（2-MI）was grown on the CC surface as an amorphous block of about1μm in length;the Ni-MOF synthesized by phthalic acid（PTA）was grown on the CC surface as flakes with a thickness of 0.5μm;the dual-ligand Ni-MOF@CC[Ni（PTA）₂（2-MI）₂]array was grown on the CC surface in a hybrid layered structure,where the flake thickness was about 0.3μm and the block was loaded in the flake-to-flake gap.The electrochemical test results showed that the specific capacitance of the composites at a current density of 2 m A/cm² was 292.2,481.6,and 548.1 F/g.The specific capacitance retention after 5000 charge/discharge cycles was for 69.1%,79.9%,and 83.9%,respectively.2.The Ni/Co-MOF@CC composite materials were obtained by in situ growth of single-ligand Ni/Co-MOF and double-ligand Ni/Co-MOF arrays on the CC surface under hydrothermal conditions by doping with Co²⁺.SEM test results showed that:the Ni/Co-MOF[Ni/Co（2-MI）₂]arrays were tightly encapsulated on the CC surface with a thick lamellar structure,and the average thickness 0.2～0.5μm;the lamellar structure of Ni/Co-MOF[Ni/Co（PTA）₂]array started to gradually unfold on the CC surface with an average thickness of 0.2～0.4μm;the Ni/Co-MOF@CC[Ni/Co（PTA）₂（2-MI）₂]array grew on the CC surface in thinner layered lamellar form with an average thickness of 0.1～0.2μm.The effect of reaction parameters on the morphology of the double-liganded Ni/Co-MOF arrays grown on the CC surface was further investigated,and the results showed that:with the increase of Co²⁺content,the Ni/Co-MOF arrays showed a change trend from thicker aggregated flakes to layered flakes;with the increase of reaction temperature,the Ni/Co-MOF arrays changed from large flakes of aggregated spherical particles to uniform layered flakes to With the increase of reaction time,the Ni/Co-MOF arrays grown on the CC surface gradually formed from tightly packed flakes to a structure with gaps between the flakes.The best morphology and coating state were obtained at the addition of 1.5mmol Co²⁺and hydrothermal reaction at 150℃for 12 h.The layered lamellar structure was formed with a lamellar thickness of 0.1～0.2μm.3.The electrochemical properties of Ni/Co-MOF@CC-1,Ni/Co-MOF@CC-2 and Ni/Co-MOF@CC-3 composites prepared with dual ligands and single ligands,respectively,were tested,and all of them exhibited the energy storage characteristics of battery-type and capacitive electrode materials,and the diffusion behavior and surface capacitance behavior contributed to the capacity of the composites at the same time.The contributions of surface capacitance of the composites were 45.9%,62.5%,and 32.5%at scan rate of 5 m V/s;the specific capacitance was 745.5,608.4,and 319.3 F/g at current density of 2 m A/cm²,and the specific capacitance retention rates were 88.2%,72.9%,and58.2%after 5000 charge/discharge cycles,respectively.Based on the CC substrate,this thesis designed to grow Ni/Co-MOF arrays in situ on its surface to construct a flexible electrode system of fully electrochemically active materials.The innovative choice of dimethylimidazole and phthalic acid dual ligands to modulate the MOF structure resulted in Ni/Co-MOF@CC composites,which exhibited good electrochemical performance and provided a new idea for the development of electrode materials with excellent performance.