Synthesis And Properties Of Transition Metal Sulfide Nanomaterials Based On Electrochemical Energy Storage And Sensing Applications

With the severity of the energy crisis and environmental pollution,researchers devote themselves to the study of the new energy storage devices.In recent years,electrochemical supercapacitor,because of its unique advantages,has aroused wide attention.In general,the electrode materials of the supercapacitor can be divided into three categories: carbon materials,conductive polymer,transition metal compounds.Among them,the transition metal compound not only depends on the electrostatic adsorption to store charge,but also takes place Faraday reaction between electrode materials and electrolyte.Therefore,transition metal compound has become the first choice of the supercapacitor electrode materials.Among of these metal compounds,ruthenium dioxide has been widely studied because of its wide voltage window,highly reversible redox reaction.But high cost limits the commercial application.So,some low cost transition metal compounds,such as Mn,Co,Ni,have become a preferred substitute.On the other hand,diabetes has become one of the world’s most dangerous diseases to people’s health.And blood glucose is a typical feature of the disease.In order to measure blood glucose,the development of glucose sensing has been greatly encouraged.Because traditional glucose sensing based on enzyme has some disadvantages,such as,low stability,high cost.So scientists devote themselves to develop non-enzyme glucose sensing with low cost,high sensitivity,and high selectivity.In recent years,nanostructure material has attracted wide attention in the field of electrochemistry,and its application in the electrochemical sensor mainly depends on the catalytic capacity of nanostructure modified electrode,which can reduce the overpotential of reaction,make it easier for dynamics,and improve the reversibility of redox reaction.Accordingly,the thesis focuses on the design and fabrication of transition metal sulfide nanomaterials,the design of electrode,and the construction of liquid system,solid supercapacitor and non-enzyme glucose sensor.Details are as follows:（1）Ternary Cu-Co sulfides,CuCo₂S₄,with an average size of 60 nm were synthesized via a simple and low-cost one-step solvothermal method.Electrochemical test results show that CuCo₂S₄ nanoparticles exhibit excellent electrochemical performances,in the 3 mol dm^-3 KOH electrolyte.At 1 Ag^-1 current density,capacitance reached 443.7 Fg^-1,and the capacitance retention rate was 83.8% after 10000 times of charge and discharge test.More prominently,the CuCo₂S₄ material and the activated carbon are respectively made into the positive and negative electrodes of the capacitor and assembled into an asymmetric supercapacitor having a high surface capacitance.At 3 mA cm^-2 current density,the surface capacitance reached 274.5 mF cm^-2,and the capacitance retention rate of the asymmetric device can remain 94.7% of the initial specific capacitance after 5000 cycles of constant current charging and discharging at different current densities.In addition,the assembled supercapacitor can be charged and then discharged to drive various electronic components.（2）The all solid state asymmetric CuCo₂S₄//AC supercapacitors was assembled by using CuCo₂S₄//AC material and activated carbon as positive and negative active materials of supercapacitor,foamed nickel as collector and polyvinyl alcohol / KOH as electrolyte.And its electrochemical performance was studied by cyclic voltammetry and constant current charge and discharge.Electrochemical test results show that the voltage window of the all-solid asymmetric CuCo₂S₄//AC super capacitor can reach 0-1.4 V and the specific capacitance is 42.7 Fg^-1 at a current density of 3 m A cm^-2.When the energy density is 11.5 Wh kg^-1,the power density is 281.3W kg^-1.In order to contrast,all solid-state symmetrical CuCo₂S₄// CuCo₂S₄ supercapacitor was assembled.（3）CuCo₂S₄ nanoparticles have a large specific surface area,high surface activity and catalytic efficiency,which can act as an electrocatalyst for oxidation of glucose.So selecting CuCo₂S₄ nanoparticles which were successfully synthesized and using the perfluorosulfonic acid membrane to immobilize CuCo₂S₄ material on the surface of the electrode.An non-enzyme glucose sensor based on CuCo₂S₄ / Nafion / GCE was constructed.Various influence factors such as pH,the loading of active substances and the working point were tested by cyclic voltammetry and chronopotentiometry.Under the optimized experimental conditions,the sensitivity of the sensor to glucose was 21.46 μA cm^-2 mM^-1,the linear range was 0.05-0.8 mmol L^-1,and the detection limit was 9.54 μM（S/N = 3）.（4）Synthesis of high aspect ratio NiS nanowire arrays by solvothermal method,which is simple and effective without the use of any surfactant,Characterization results reveal that the as-obtained NiS nanowire belongs to rhombohedral phase with higher aspect ratio.NiS nanowire arrays supported by the foamed nickel exhibited excellent electrochemical performance as a binderless electrode,with a specific capacitance of 10.3 F cm^-2 at a current density of 20 mA cm^-2 and a good electrochemical performance in the 3 mol dm^-3 KOH electrolyte solution and the cycle stability（79.0% after 8000 cycles）.