Synthesis Of Co,Ni Sulfide With Hierarchical Structure Based On MOFs And Their Electrochemical Proformances

Metal organic frameworks（MOFs）,as a kind of metal and organic ligands to construct emerging three-dimensional materials,with its specific surface area,stability,channel structure and unique components,have been widely used in gas adsorption and storage,gas separation,fluorescence,sensor and so on.Via MOFs as the precursor or template,design and synthesis novel structure functional nanomaterials,which are applied in energy storage and transformation,such as electrochemical catalysis,lithium ion batteries and supercapacitors,to solve our currently faced with the problem of energy crisis and environmental pollution is of great significance.The unique properties of metal sulfides determine its excellent performance as electrode material for supercapacitors.In this dissertation,we design and synthesize Co,Ni bimetallic sulfide nanomaterials with hierarchical structure based on MOFs,and probes those materials in the application of supercapacitors.The details are as follows:1.This study designed and synthesized Ni-Co@Co-Co PBA with core-shell structure,wherein the Ni-Co PBA crystal was as core,and the shell of Co-Co PBA was grown.With this novel MOFs as a precursor,a simple solvothermal method is used to transform it into a hollow double-shelled Ni₃S₄@Co₉S₈.In the same way,we synthesized Ni S and Co₉S₈with a single shell by Ni-Co PBA and Co-Co PBA as the template separately.The relationship between electrochemical properties and structure was studied by using three materials as electrode materials for supercapacitors.The test results show that compared with the single-shelled Co₉S₈,the double-shelled Ni₃S₄@Co₉S₈ has a significantly higher specific capacitance.Compared with the single-shelled Ni S,Ni₃S₄@Co₉S₈ showed better rate performance.2.It is very important to improve the performance of electrode material by constructing bimetallic sulfide with core-shell structure and combining the characteristics of different metal sulfide.We first synthesized ZIF-67 as the precursor and grown Si O₂ in the surface,and then high temperature calcined in Ar atmosphere to obtain Co/N-C@Si O₂.Finally,Na₂S as sulfur source,Co₃S₄/N-C@Ni₃S₄ with a hierarchical structure was successfully achieved by solvothermal method.In contrast,N-C@Ni₃S₄ and Co₉S₈/N-C were designed and synthesized.The relationship between electrochemical properties and structure was studied by using three materials as electrode materials for supercapacitors.The results show that specific capacitance and rate performance of core-shelled structure Co₃S₄/N-C@Ni₃S₄ are significantly improved than that of N-C@Ni₃S₄ and Co₉S₈/N-C.3.The synergy in the nickel and cobalt ions of the ternary sulfides（Ni Co₂S₄）can provide more oxidation types,and the improvement of electrochemical performance is benefited to more than that of binary sulfide（Co_xS_y,Ni_xS_y）.First,this study synthesized Ni-Co PBA at room temperature,and after growing a layer of Si O₂,the Ni-Co PBA@Si O₂ with core-shelled structure was obtained,which was further converted into a hollow double-shell via being calcined in air condition.The hollow double-shelled structure was successfully prepared by a solvothermal method.The relationship between electrochemical properties as electrode material for supercapacitor and structure was studied.The test results showed that compared with Ni Co₂S₄,the specific capacitance and cycling proformance of double-shelled Ni Co₂S₄@Ni₃S₄ was significantly improved.