Synthesis Of Two-dimensional Nanoporous Transition Metal Complexs And Their Electrochemical Energy Storage Property

Effectively solving future energy problems is an important cornerstone for the sustainable development of human society and economy.Supercapacitors?SCs?,also known as electro-chemical capacitors,are considered as a most promising type of devices for next-generation energy storage in view of the advantages of their high power density,fast charge and discharge rate,excellent cycle stability and safety.One of the crucial challenges for fabricating SCs device is to find electrode materials that have excellent electronic conductivity,high mass capacitance,large accessible surface areas,and high stability in electrochemical processes.Two-dimensional nanoporous transition metal complexs material,which has the advantages of large specific surface area,rich electrochemical reactive sites and easy-modification of organic ligands.It may have become a very competitive electrode material for supercapacitors in the future.In this paper,a series of two-dimensional nanoporous transition metal complexs were prepared by hydrothermal synthesis using polycarboxylic acid?1,3,5-benzentricarboxylate,H₃BTC?and amino acid?glycine,Gly?as organic ligands,transition metal cobalt and nickel as metal sources.The composition and structure of the sample were determined by XRD,XPS and FT-IR tests;and the morphology and microscopic characteristics of the product were observed by field-emission scanning electron microscope?SEM?and transmission electron microscope?TEM?tests;physical data such as specific surface area and pore size of the reaction product were analyzed by N₂ adsorption/desorption;the electrochemical workstation CHI760 was used to study the performance of the supercapacitor in detail and systematically.This paper mainly includes the following two aspects:Firstly,two-dimensional nanoporous nanosheets of M-1,3,5-Benzentricarboxylate metal-organic frameworks for an anode material of supercapacitors.A series of 2D M-BTC?M=Co,Ni and Co-Ni?MOFs such as Co-BTC,Ni-BTC and Co-Ni-BTC have been successfully synthesized by simply varying the metal precursors.The products all have similar highly uniform 2D thin nanosheets with an open and porous hierarchical structures,it is noted that the density of 3D cross-linking of Co-Ni-BTC is much higher than Co-BTC and Ni-BTC.The specific surface areas of the different metal based isostructural MOFs follow the order of Co-Ni-BTC(144.67 m²?g^-1)>Ni-BTC(87.28 m²?g^-1)>Co-BTC(31.79 m²?g^-1).The calculated specific capacitances of Co-BTC,Ni-BTC and Co-Ni-BTC are 1321.5,1465.0 and 1751.3 F?g^-1,respectively,in a three-electrode mode.The ASC of Co-BTC//AC,Ni-BTC//AC and Co-Ni-BTC//AC provided a high energy density of 24.50,27.33 and 35.5 Wh·kg^-1 at power density of 900 W·kg^-1,and remained 15.75,10.00 and 13.75 Wh·kg^-1 at 9000W·kg^-1,respectively.After 10000 cycles,the specific capacitance of the Co-BTC//AC,Ni-BTC//AC and Co-Ni-BTC//AC device were maintained at 92.39,93.92 and 98.29%of its initial specific capacitance,which reveals an better cycling stability performance of M-BTC MOFs//AC device.Secondly,synthesis and supercapacitors properties of two-dimensional nanoporous thin sheets of Ni-Glycine complexes materials.The product has been prepared by a facile and cost-effective hydrothermal method at a temperature of 220°C for 12 h,which possess a well-defined and interconnected 3D network with a lot of intricate and continuous pores.From the N₂ adsorption-desorption isotherm,the BET specific surface area is estimated to be 234.13 m²·g^-1,whose pore-size distributions peak was located at the range of 4-8 nm.The obtained Ni-Glycine nanostructures delivered a higher mass specific capacitance of 2171.71 F·g^-1.With the current density increased from 1 to 10 A·g^-1,the specific capacitance of electrode materials showed a trend of decreasing gradually,which still retained 80.77%of the initial capacitance.And an ASC device of Ni-Glycine//AC delivered the energy density of 35.05,29.66,24.80,21.60,19.00 and 16.75 Wh·kg^-1 at the power densities of 900,1800,3600,5400,7200 and 9000 W·kg^-1.Furthermore,the device of Ni-Glycine//AC retained a capacitance in excess of 94.6%after 10000 cycles,indicating a good cycling life.