Study On The Synthesis And Electrochemical Performances Of Nickel Sulfide Nanomaterials

This thesis mainly focuses on the design and the synthesis of the nickel sulfide micro/nanomaterials for the applications as high performance supercapacitor materials.The main research contents are as follows:1.The pure Ni₃S₂ nanostructures were synthesized directly on nickel foam?NF?substrate through one-step solvothermal method with nickel nitrate and thiourea serving as raw materials.The morphologies and phase of Ni₃S₂ were characterized by using X-ray diffraction?XRD?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?and transmission electron microscopy?TEM?.The optimum synthetic conditions for the pure Ni₃S₂ nanostructures have been investigated.The samples produced at different conditions directly used as the work electrodes to examine their supercapacitor properties through a series of electrochemical testing methods,such as cyclic voltammetry,galvanostatic charge/discharge,AC impedance and cycle stability.The experimental results show that the pure Ni₃S₂ with the 3D nanoscale thin slices interconnected into an open porous network structure is prepared at the growth temperature of 180?and growth time of 12 h.As cathode material of supercapacitors,the prepared Ni₃S₂ with high specific capacitance and good cycling stability has the best electrochemical performance in all experimental conditions.Which Show a higher specific capacitance of 1356.8 F g^-1 at a current density of 1 A g^-1 and an excellent cyclic performance with 90%capacity retention after 3000 cycles at a current density of 5 A g^-1.The results Ni₃S₂ structure is a very excellent supercapacitor electrode material.2.The Ni?OH?₂ was successfully compounded on pure Ni₃S₂ material by a solvothermal method.The structure of the obtained Ni₃S₂/Ni?OH?₂ nanocomposites were characterized,and the electrochemical performance were tested.The experimental results show that the morphology of the composite has been changed from nanoscale to nanometer ultra-thin slices compared with the pure Ni₃S₂.The nanometer ultra-thin slices of the Ni₃S₂/Ni?OH?₂ form ultrathin nanoscale walls,and a large number of ultrathin nanoscale walls are interconnected to form an ordered three-dimensional porous network structure.The study shows that the structure with more pores is very beneficial to the infiltration of the electrolyte and improves the effective use area of Ni₃S₂/Ni?OH?₂ as the electrode material.Compared with the simple pure Ni₃S₂ material,Ni₃S₂/Ni?OH?₂ composite nanomaterials have high specific capacitance(1900 F g^-1)and excellent cycle performance?98%?.As the composition of Ni?OH?₂ with Ni₃S₂,through the synergistic reaction of two materials,the resistance is effectively reduced,and the specific capacity and the cyclic stability are dominant improved.It shows that the nanometer ultra-thin slices with porous of Ni₃S₂/Ni?OH?₂ composite electrode material has potential application value.3.NiS and Zn-doped NiS powder samples were successfully synthesized by a simple solvothermal method under the same conditions.The structural characteristics and electrochemical properties were studied.The results indicate that the pure NiS and Zn-doped NiS have good crystallinity,the doping of Zn does not change the crystal direction but embed into the crystal lattice of NiS.The SEM images of NiS show that the surface structure of the pure NiS is smooth and has a slight agglomeration,and the surface structure of Zn-doped NiS becomes more rough,dispersed and uniform.The test results of BET indicate that Zn-doped NiS has larger specific surface area and more uniform structure size.The electrochemical performance results show that the Zn-doped NiS nanoarchitectures delivered excellent specific capacitance(894.3 F g^-1)and an excellent cyclic performance?94.5%?.Therefore,Zn doped NiS materials have good electrochemical properties and wide application prospects.