| In this paper,metallic cobalt nickel nitrides and sulfides were prepared by hydrothermal and solvothermal method based on different post-treatment methods,cobalt nickel nitrides obtained by high-temperature annealing of cobalt hydroxide and nickel hydroxide precursors under ammonia atmosphere,cobalt nickel sulfides were synthesized by two-step solvothermal method.The microscopic morphology of the material was characterized by field emission electron microscopy,its elemental distribution was characterized by Energy Dispersive Spectroscopy（EDS）.The crystal structure compositions of the material were analyzed by X-ray diffractometer,and the chemical composition and valence state were analyzed by X-ray photoelectron spectroscopy.Their electrochemical properties were measured by the cyclic voltammogram,the galvanostatic charge-discharge to study the capacitive behaviors.The main work of the thesis summarized as following:After one-step hydrothermal method,and then annealed at high temperature under ammonia atmosphere,metallic cobalt nickel nitrides supercapacitor electrode materials in situ loaded on carbon cloth substrate were finally obtained to realize the preparation of binder-free flexible electrodes.EDS proved the successfully doping of N elements.The nano-structure of prepared electrode was grass-like,which is beneficial to ion diffusion and mass transfer.As a comparison,Co2N and Ni3N electrode materials were prepared,and metallic cobalt nickel nitrides exhibited excellent electrochemical performance.The electrochemical experimental results showed the cobalt nickel nitride electrode annealed at 350℃had best electrochemical performance in 3 M KOH electrolyte with area specific capacitance up to 3586.9 mF cm-2.The capacitance retention was99.96%after 3000 cycles,showing an excellent cycling performance.A series of cobalt nickel sulfides with different molar ratios of metal sources were successfully prepared by two-step solvothermal method on the carbon cloth.Compared with cobalt nickel oxides,the bimetallic nickel cobalt sulfides showed excellent electrochemical performance,which was attributed to the lower electronegativity of S atoms than O atoms in the sulfides,which promoted the electron transfer.The experimental results demonstrated that the electrochemical performance of bimetallic nickel cobalt sulfides was superior to that of cobalt sulfides and nickel sulfides due to the synergistic effect of cobalt and nickel ions.Among the three-electrode systems,the cobalt and nickel bimetallic sulfides material（molar ratio Co:Ni=2:1）had the best electrochemical performance with an area specific capacitance of 4789.0 mF cm-2 at a current density of 1 mA cm-2.The prepared asymmetric supercapacitor exhibited an operating voltage range to 1.4 V,which was worked with electric double layers and pseudocapacitance.The area specific capacitance of asymmetric supercapacitor was 128.0 mF cm-2 at a scan rate of 10 mV s-1. |
