Synthesis Of Transition Metal Sulfides With Hierarchical Structures As Self-supported Electrodes For Electrochemical Energy Storage

Transition metal compounds are considered to be an ideal pseudocapacitive electrode material for supercapacitor due to their high theoretical capacitance and electrochemical activity,but their low conductivity limits their electrochemical properties in practical application.In this work,the strategies of improving the electrochemical properties of transition metal compounds are intensively studied,such as construction of three-dimensional hierarchical structure,defect regulation and so on.In addition,light irradiation is introduced in electrochemical tests to study the photo-enhanced electrochemical behavior in transition metal electrode materials.The main research conclusions are as follows:（1）Copper foam supported ternary Ni-Co-Cu chalcogenides nanosheets confined in nanowire array as a self-supported electrode material were synthesized by in situ growth and several hydrothermal processes.Benefitted from the successful construction of the hierarchical structure and the synergy of Ni,Co,Cu sulfides,the as-prepared material shows excellent electrochemical properties.The specific capacitance of the electrode material can reach 3.6 F cm^-2 at a current density of 5 m A cm^-2.In addition,when employed as electrode materials in asymmetrical supercapacitor cell,the Ni-Co-Cu-S ternary chalcogenides material has delivered a high specific capacitance of 746.7 m F cm^-2 with a good retention of 97.1%at a very high current density of 100 m A cm^-2.（2）Copper foam supported Cu₂S nanosheet array with rich sulfur vacancies was prepared by hydrothermal vulcanization and surface etching processes.Due to the construction of the hierarchical structure and the enrichment of sulfur vacancies,the electrochemical properties of the as-prepared materials have been significantly improved.Moreover,due to the good photothermal conversion characteristics of the materials,the energy storage process of all samples has been enhanced under continuous light illumination,and their specific capacitance has been significantly improved by 15.0%-38.0%,which illustrates the feasibility of using the light absorption and conversion capacity of the electrode materials for photo-enhanced electrochemical energy storage.