Preparation And Electrocatalytic Hydrogen Evolution Performance Of Cobalt Selenide Nanocomposite

As the storage of fossil energy continues to decrease,the development and utilization of hydrogen energy has gradually entered people’s vision.At the same time,the research as an electrochemical catalyst for preparing high-purity hydrogen has also received more and more attention.In this thesis,CoSe₂/GO,Co@CoSe₂/NC and CoSe/Mo Se₂ nanocomposites were synthesized as electrocatalytic hydrogen evolution catalysts by a simple hydrothermal method.The phase composition of the composite material was determined using X-ray diffractometer and X-ray photoelectron spectroscopy,and the microstructure of the composite material was observed using scanning electron microscope and transmission electron microscope.Finally,the catalytic and cyclic performance of the material were tested by electrochemical methods such as scanning voltammetry,cyclic voltammetry,and AC impedance.The specific research can be divided into the following three aspects:1. Graphene oxide was prepared using the modified hummer method,then cobalt ions were adsorbed to the surface of graphene by microemulsion method to generate cobalt hydroxide/graphene precursor.Finally,the CoSe₂/GO was obtained by hydrothermal selenization of the precursor.Transmission electron microscopy found that CoSe² was uniformly dispersed on the surface of graphene,and the particle size of CoSe² prepared by microemulsion method was significantly reduced.After the electrochemical test,in acidic electrolyte,when the current density reaches 10mA/cm²,the composite overpotential is only 202mV,and it has good cycle stability.2. The ZIF-67 monomer was prepared using traditional methods,then the Co/NC precursor was obtained by calcination and annealing at 700℃.Finally,the target product Co@CoSe/NC was obtained by hydrothermal selenization of the precursor.After applying a magnetic field,the composite material was found to be magnetic,and after observation by transmission electron microscope,it was found that the composite material still retained the original polyhedral structure of ZIF-67,and did not disintegrate by hydrothermal processes.After the electrochemical test,in acidic electrolyte,when the current density reaches 10mA/cm²,the composite overpotential is 192mV,and the slope of Co@CoSe/NC tafel curve is only 20mV/dec.3. Cobalt selenide was synthesized through the first step of hydrothermal,and then the molybdenum diselenide was grown on the surface by using the cobalt selenide as the carrier through the second step of hydrothermal.Finally,the CoSe/Mo Se₂ was obtained.It can be clearly seen from the transmission electron microscope and scanning electron microscope pictures that cobalt selenide and molybdenum diselenide are both sheet-like structures,and a heterostructure between cobalt selenide and molybdenum diselenide is also found at high magnification.After electrochemical tests,the composite exhibited excellent catalytic activity in both acidic and basic conditions.When the current density reaches 10mA/cm²,the over potentials of CoSe/Mo Se₂ in acidic and alkaline are 192mV and 115mV respectively.