Preparation And Supercapacitor Performance Of Heterometallic Nano-MOF And Derivatives

Metal organic frameworks?MOF?,as an organic-inorganic material,are characterized by structure diversity,adjustable pore size,large specific surface area and various ligands.The application of MOF as electrode materials in supercapacitors has been widely concerned by researchers.However,the traditional single metal MOF generally has poor conductivity and high resistance,which hinders their application as electrode materials.Therefore,this paper is devoted to the studying of heterometallic MOF and their derivatives,and to test their supercapacitor performance.The content mainly includes the following parts:The Ni/Co-nicotinate MOF-based bricks were successfully transformed into mesoporous Ni₂CoS₄ by thioacetamide.The electrochemical test results reveal that Ni₂CoS₄ has excellent electrochemical properties,and its'specific capacity was 1466.8 F g^-1 at current density 1 A g^-1.In addition,an asymmetric supercapacitor?ASC?was assembled by Ni₂CoS₄ material and activated carbon?AC?.The Ni₂CoS₄//AC ASC exhibits an energy density was 37.8 Wh kg^-1 at 1066.8 W kg^-1.And the capacitance retention of Ni2CoS4//AC ASC was 113.7%after 10000 charge-discharge cycles.The results shwed that Ni₂CoS₄//AC ASC had excellent chemical stability.Bimetallic Ni/Co-MOF with flower-like structures assembled from nanosheets were synthesized by etching Ni-MOF microspheres with Co?NO₃?₂ in ethanol solution and adjusting the mass ratio of Co?NO₃?₂·6H₂O to Ni-MOF and the reaction time.Among them,the optimized Ni/Co-MOF-5showed superior electrochemical performance with high specific capacitances of 1220.2 F g^-1 and986.7 F g^-1 at current densities of 1 A g^-1 and 10 A g^-1,respectively.Furthermore,in order to expand the development space of MOF materials,the Ni-Co-S nanoparticles were obtained by sulfuring Ni/Co-MOF-5 with thioacetamide.The specific capacitance of Ni-Co-S electrode was 1377.5 F g^-1at current densities of 1 A g^-1 and it shows good rate capability.The retention was up to 93.7%even after 3000 cycles.In addition,the electrochemical test results of Ni/Co-MOF-5//AC ASC and Ni-Co-S//AC ASC devices show that high energy density,power density and good cycling stability.The Ni/Co-precursors@Ni-MOF arrays on Ni foam were perepared from Ni-MOF precursors.Then Ni/Co-precursors@Ni-MOF arrays were vulcanized and thermally annealed to prepare the lollipop-type NiCo₂S₄@Ni₃S₂ and NiCo₂O₄@NiO inorganic nanoarrays.The NiCo₂S₄@Ni₃S₂ and NiCo₂O₄@NiO nanoarrays were electrochemically tested in KOH solution.The NiCo₂S₄@Ni₃S₂and NiCo₂O₄@NiO electrodes exhibited specific capacitances of 1536.8 and 1033.4 F g^-1 at 1 A g^-1,respectively.Furthermore,we assembled NiCo₂S₄@Ni₃S₂//AC ASC and NiCo₂O₄@NiO//AC ASC devices.The energy density of NiCo₂S₄@Ni₃S₂//AC ASC device was 35.3 Wh Kg^-1 at power density of 724.9 W Kg^-1.And the energy density of NiCo₂O₄@NiO//AC ASC device was 24.5 Wh Kg^-1 at power density of 720.6 W Kg^-1.The capacitance retention of NiCo₂S₄@Ni₃S₂//AC ASC and NiCo₂O₄@NiO//AC ASC devices can still reach up to 97.4%and 113.5%after 10000 charge-discharge cycles at current density of 10 A g^-1,respectively.These results indicate that the interated nano-array structure and bimetallic sulfides or oxides can improve the electrochemical properties of materials.In conclusion,the paper is devoted to regulating and synthesizing novel heterometallic MOF materials,and seeking the best conversion method to transform MOF into metal oxide/sulfide,in order to improve the electrochemical properties of materials.