Synthesis And Electrochemical Properties Of Nickel Sulfide Electrode Materials

Due to issues of energy shortage and environmental pollution today,the development of electrocatalyst and electrochemical energy storage devices plays an important role in our life.Nickel sulfide(NiSx)is a kind of important battery-like electrode material with high conductivity and specific capacitance,but its rate performance and cycling stability are still poor.When being used as electrocatalyst,its catalytic activity is still not as good as that of most precious noble-metal-based catalysts.Consequently,this thesis aims to improve the specific capacitances and catalytic ability of NiSx by appropriate structure design.The main work of this thesis is as follows:Hierarchical NiSx hollow microspheres can be successfully synthesized with a template-free method using a-Ni(OH)2 microspheres as a precursor by calcination and sulfidation.The effect of different thermal treatment temperatures on the electrochemical performances of NiSx is also discussed.Electrochemical tests show that the NiSx prepared from Ni intermediate spheres at 300 ℃ show a high specific capacity.A hybrid capacitor is assembled by using NiSx-300 as positive electrode and activated carbon as negative electrode,which exhibits a good cycling stability,meanwhile high energy density and power density can be obtained.NiSx hollow microspheres can be also used as an electrocatalyst to study the catalytic activity of NiSx.It demonstrates that NiSx-300 exhibits efficient OER and HER performances due to its abundant electrocatalytic active sites and high specific surface area.At the same time,NiSx-300 is used as the bifunctional electrocatalyst to build a two-electrode system electrolytic cell.The good cycling stability and enhanced electrocatalytic activity make NiSx-300 a potentially efficient electrocatalyst.NiS with a three-dimensional flower-like structure is synthesized using β-Ni(OH)2 as a precursor by a simple hydrothermal method and the electrocatalytic activity of OER is studied.The results show that the unique three-dimensional flower-like structure of NiS can expose much more active sites,and its high porosity can benefit the proton/charge transfer.Therefore,the OER reaction kinetics are further promoted.