Control Two-dimension Transition Metal Of Cobalt Sulfide Structure Toward Supercapacitor And Oxygen Evolution Reaction

As a basic chemistry subject,electrochemistry plays an important role in solving the current energy crisis and environmental pollution.With the increasing demand of people and industrial production for the effective utilization of green energy,the electrochemical technology has been fully developed,especially electrochemical energy storage and catalytic electrolysis of water,in which supercapacitors and electrocatalytic oxygen production have received extensive attention.This dissertation designs and synthesizes three special structures for two-dimensional materials by adjusting the structure of two-dimensional transition metal sulfide materials.There are an interlaminar NiCo₂S₄-Co₉S₈ heterostructure,an vertical in-plane edge in cobalt sulfur heterostructure(Co_1-xS/Co₉S₈),and a flower-like Co_1-xS.The phase structure and surface valence states of the electrode materials and catalysts were characterized by XRD and XPS.The morphology and structure of the nanoelectrocatalysts were observed by TEM and HRTEM,and semi-quantitative analysis was performed by EDX-Mapping.A series of multi-factor conditioning materials proposes the possible formation mechanism of these unique nanostructures.Finally,the performance of the synthesized electrode materials and catalysts in supercapacitors and electrocatalytic oxygen evolution was tested by electrochemical techniques.The performance of the materials was fully examined by a variety of electrochemical methods,and the intrinsic characteristics of the materials were analyzed in combination with their own topography.Relevance design can provide ideas for further material improvements.?1?NiCo₂S₄-Co₉S₈ nano-electrode material with heterodisperse and inter-layer heterostructure was synthesized by designing the different of raw materials concentration produced different sulfides in the synthesis process.The struture of precipitate that small lamellar material is loaded on the large layered material,avoid the large areas of the two-dimensional material stacked on each other,which can expand each layer to form multi-level pores.Due to the existence of these structures,it has good chemical energy storage performance.At a current density of 2 A·g^-1,the specific capacitance of material reaches 1250 F·g^-1,and then at 10 A·g^-1,the specific capacitance value still has 1222 F·g^-1,which show a stable structure and multi-level pores.It is the key for the material to hold a higher specific capacitance at high current densities.?2?A simple one-step hydrothermal synthesis of heterostructure Co_1-xS/Co₉S₈ with the edge vertical in-plane is easily produced,while Co_1-xS is generated at high concentrations and Co₉S₈ is preferentially generated at low concentration and controlled by the action of ethylene glycol.Co₉S₈ grows on Co_1-xS to form an vertical in-plane edge structure,which fully exposes the active edge catalytic sites and greatly enhances the catalytic activity.The overpotential of Co_1-xS/Co₉S₈ at 10 mA·cm^-2 is only 275 mV and the Tafel slope is only 30mV·decade^-1,the reaction rate of existing electrocatalytic oxygen precipitation has been greatly increased.Thus,the electrocatalyst with vertical in-plane edge structure can provide a better reference for other catalyst designs.?3?The two-dimensional material is designed to grow on a zero-dimensional material to form a three-dimensional structure as a flower-like shape of Co_1-xS,which effectively avoids the stacking of two-dimensional materials and forms a solid pore.It can effectively avoid the problem that the mutual stacking between monomer catalysts.In addition,the particle size of Co_1-xS particles can be freely controlled by adjusting the ratio of water in the mixed solvent,the amount of surfactant,and the concentration of raw materials.By optimizing the structure,Co_1-xS has a good initial overpotential?320 mV?,Tafel slope of 55mV·decade^-1,good stability and conductivity.