The Capacitive Properties Based On Metal Organic Framework And Their Derived Nanostructures

Supercapacitors is a kind of practical and efficient energy storage devices.Electrode material directly influence the electrochemical properties of Supercapacitors.The MOFs,with large specific surface area,controllable pore structure and open metal active sites,have a good candidates in high-performance supercapacitors.In this paper,we prepared nickel（Ⅱ）1,3,5-benzenetricarboxylate metal-organic frameworks/Multi-walled carbon nanotubes（Ni（btc）/MWCNTs）,trithiocyanuric acid-nickel(（Ni（TCY））and ZIF-67.We also prepared metal sulfide from(Ni（TCY）and ZIF-67 and investigate the capacitive properties of the MOFs and their derived metal sulfide.The main works is concisely described as followed:（1）In this work,the hierarchical flower-like nickel（Ⅱ）1,3,5-benzenetricarboxylate metal-organic frameworks/Multi-walled carbon nanotubes（Ni（btc）/MWCNTs）was synthesized through a facile hydrothermal method.The products were characterized by scanning electron microscope（SEM）,X-ray diffraction（XRD）,fourier-transform infrared（FT-IR）and N2 sorption experiments（BET）.The experimental results showed that the incorporation of MWCNTs can induce the transformation of spherical Ni（btc）into the flower-like structure,improving the specific surface area and the conductive properties of Ni（btc）/MWCNTs.The electrochemical studies displayed that Ni（btc）/MWCNTs had a higher specific capacitance and cycling performance than that of the single component for Ni（btc）.The specific capacitance of Ni（btc）/MWCNTs is estimated to be 916 F g^-1 at 2 A g^-1 and 711 F g^-1 at 10 A g^-1,respectively.It also exhibits an outstanding long-term cycling stability,retaining 93.5% of its initial specific capacitance after 1000 charge-discharge cycles at a current density of 10 A g^-1.（2）In this work,the spherical Ni（TCY）was prepared successfully by using Ni（NO₃）₂·6H₂O and trithiocyanuric acid（TCY）ligands as raw material.As a precursor,Ni（TCY）was transferred to pure phase metal sulfide（Ni S）nanoparticles by thermal annealing for the first time.These materials were characterized by SEM, XRD,TEM and XPS.The results showed that the specific capacitance of the Ni S nanoparticles only changed from 1493 F g^-1 to 1160 F g^-1 when the current density increased from 4 to 20 A g^-1,which is significantly higher than the 1111 F g^-1 to 840 F g^-1 for Ni（TCY）in the same conditions.The specific capacitance of the Ni S nanoparticles remains 85.4% after 2500 cycles at the high current density of 10 A g^-1.（3）In this work,we prepared ZIF-67 in room temperature using Co（NO₃）₂·6H₂O and 2-methylimidazole as raw material.Then,the nickel nitrate hexahydrate and thiacetamidethe were added into the ZIF-67 ethanol dispersion in turn.Afer that,the mixed solution was refluxed at 90℃ for 1h to obtain the bimetallic Co-Ni sulfide（Co-Ni-S）hollow polyhedron.Their morphologies were characterized by SEM,XRD,TEM and EDS.The capacitive behavior of Co-Ni-S was investigated by cyclic voltammetry,chronopotentiometry and electrochemical impedance spectroscopy.The results showed that the Co-Ni-S hollow polyhedron displayed high specific capacitance which had 1890 F g^-1 at 4 A g^-1 and 1535 F g^-1 at 20 A g^-1,showing a good rate capability of 81.2%.At the same time,the bimetallic Co-Ni-S also exhibited excellent long-term cycling stability,retaining 89.3% of its initial specific capacitance after 1000 charge-discharge cycles at a current density of 10 A g^-1.