Nickel And Cobalt Metal-Organic Frameworks And Its Application In Supercapacitors

Metal-organic frameworks?MOFs?are a new type of porous,high-specific-area,and adjustable-structure materials.They have obvious advantages as supercapacitor materials.However,the shortcomings of MOFs,such as poor conductivity,small specific capacitance and low energy density,have affected its application in supercapacitors.This paper uses Ni?NO₃?₂·6H₂O as the metal center,and terephthalic acid as an organic ligand to prepare Ni-MOF materials,and composites them with carbon nanotubes?CNT?as cathode materials for electrochemical performance testing.The effect of functional groups on the electrochemical performance of Ni-MOF materials was explored by changing the functional groups on terephthalic acid.By adjusting the content of metal Co,the influence of Co metal content on the electrochemical performance of bimetal MOFs was explored.The content of this article is as follows:1.Ni-MOF-NO₂,Ni-MOF,and Ni-MOF-NH₂ were prepared by DMF solvothermal method using 2-nitroterephthalic acid,terephthalic acid,and 2-aminoterephthalic acid,respectively.Physical and electrochemical characterization using SEM,EDS,XRD,and BET showed that Ni-MOF-NH2 has a thin plate-like structure,a high specific surface area,an excellent mesoporous structure,and excellent crystallinity.These structural changes are conducive to improving the electron transfer rate in MOFs materials.Electrochemical tests show that the specific capacitance of Ni-MOF-NH₂ at a high scan rate of 100mV S^-11 and a potential window of 0-0.45 V is as high as 1024.4 F g^-1,which is much higher than Ni-MOF-NO2(353.9 F g^-1)and Ni-MOF(399.5 F g^-1).At a current density of 1A g-1,Ni-MOF-NH2 shows a high specific capacitance of 1473 Fg^-1,which is also much higher than Ni-MOF-NO2(750F g^-1)and Ni-MOF(1010 Fg^-1).In short,the introduction of the electron donor group-NH ₂ not only affects the morphology and specific surface area of the MOF material,but also increases the electron cloud density of the metal active center,activates the metal center Ni and reduces the polarization of the electrode.This is an effective method to improve the electrochemical performance of Ni-MOF materials.2.Based on the work of 1,2-aminoterephthalic acid was selected as the organic ligand.Ni-Co bimetal MOFs materials were also prepared by the solvothermal method.Bi-metal MOFs(Ni-Co-MOF,Ni-Co_1.5-MOF and Ni-Co₂-MOF)with different Co content were prepared by changing the content of metallic Co.Characterization of physical and electrochemical properties by SEM,TEM,BET and XRD showed that Ni-Co-MOF has a thin nanoplatelet structure and high specific surface area,excellent pore structure and good crystallinity.These structures are conducive to improving the transfer rate of electrons in MOFs.Through the electrochemical performance test,Ni-Co-MOF has a specific capacitance of 1081.1 F g^-11 at a scan rate of 100mV S^-1,which is much higher than Ni-Co_1.5-MOF(709.2 F g^-1)and Ni-Co₂-MOF(493.7 F g^-1).It exhibits an ultra-high specific capacitance of 2350.4 F g^-11 at a scan rate of1mV S^-1.This proves that metal doping is an effective way to improve the electrochemical performance of MOFs materials,and controlling the content of doped metals can improve the performance of the original materials.