| To tackle the global challenges of climate change and carbon neutrality brought about by increasing energy consumption and worsening environmental problems,clean,green,renewable and sustainable energy storage and conversion devices are gaining significant momentum worldwide.Being one of the most potential electrochemical energy storage devices,supercapacitors（SCs）have found wide applications in various fields such as hybrid vehicles,portable electronic devices,and industrial energy management due to their remarkable features including high power output,fast charge time,extended lifespan,superior safety and reliability.Therefore,the development of high-performance electrode materials is of great significance for the research and application of SCs.As a new two-dimensional（2D）layered topological material,Bi2Se3is an ideal negative electrode material for supercapacitors due to its high carrier mobility,high conductivity and high theoretical capacity.However,how to efficiently and quickly prepare 2D Bi2Se3 is an urgent problem to be solved.Under this context,we use electrochemical exfoliation method to synthesize 2D ultra-thin Bi2Se3 nanosheets,based on which an asymmetric aqueous supercapacitor was assembled along with Ni Co2S4 anode prepared by hydrothermal method.The electrochemical characterization shows that Bi2Se3 as a negative electrode material exhibits excellent energy storage capability.The main work includes the following three parts:1.Fabrication and characterization of 2D Bi2Se3.Ultra-thin 2D Bi2Se3nanosheets were prepared by electrochemical exfoliation,the morphology and structure of which were thoroughly characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,atomic force microscopy（AFM）and X-ray diffraction（XRD）.The results show that Bi2Se3with a thickness of about 2-5 nm were successfully fabricated.2.The electrochemical properties and energy storage mechanism of 2D Bi2Se3.Through tests including cyclic voltammetry（CV）,galvanostatic charge-discharge（GCD）and the electrochemical impedance spectroscopy（EIS）,the electrochemical performance of Bi2Se3 negative electrode is characterized.By calculating the slope of logarithmic peak current（log（i））and logarithmic sweep rate（log（v））,the energy storage mechanism of Bi2Se3 is further explored.The results show that when Bi2Se3 is used as the negative electrode material,the specific capacity of the supercapacitor is as high as662.5 F/g at the current density of 1 A/g,and the charge storage mechanism of Bi2Se3is mainly controlled by capacitive mechanisms,the EIS test show that Bi2Se3 has fast electron transfer rate and high conductivity.3.Fabrication and electrochemical performance of asymmetric supercapacitor Bi2Se3//Ni Co2S4.The asymmetric supercapacitor Bi2Se3//Ni Co2S4 was assembled,and its electrochemical performance and working mechanism were thoroughly explored.The results show that when the current density of Ni Co2S4 is 1A/g,the specific capacity is as high as 1700 F/g.The charge storage mechanism of Ni Co2S4 is mainly controlled by capacitive mechanisms.The assembled asymmetric supercapacitor Bi2Se3//Ni Co2S4 ASC device exhibited a high energy density of 48Wh/kg at the power density of to 800 W/kg,and can successfully power Pe LED,temperature and humidity sensors,alarm clocks,etc. |
