Preparation And Modification Of VS₂ And Its Electrocatalytic Activity For Hydrogen Evolution

Energy is an indispensable resource for human survival.Due to the excessive development and utilization of human beings,we are facing an energy crisis.The fossil energy that human beings depend on is non renewable,and the environmental problems caused by the use of fossil energy need to be solved.Hydrogen,as an efficient and clean environmental protection energy,only generates water after combustion,which is considered as an effective alternative to fossil energy.Theoretical research found that the technology of preparing hydrogen by electrolyzed water is considered to be one of the most effective ways.However,the biggest problem of this technology is the high power consumption,which is mainly due to the high hydrogen evolution overpotential of the electrolytic electrode.Therefore,it is particularly important to study how to reduce the hydrogen evolution overpotential to reduce the energy consumption of electrolysis.Although platinum is an ideal catalyst for hydrogen evolution reaction,precious metals are rare resources on the earth,which can not meet the practical needs of large-scale hydrogen production.Therefore,the preparation of efficient and inexpensive hydrogen evolution catalysts has become the main research topic.Transition metal disulfides?TMDs?have great research value and potential as catalysts for hydrogen evolution.Molybdenum disulfide?Mo S₂?is widely used as catalyst for electrolyzing water,while vanadium disulfide?VS₂?is rarely used for electrocatalytic hydrogen evolution.Therefore,this paper mainly studies the preparation and modification of vanadium disulfide in order to improve the activity of the whole catalyst.The research content of this paper is as follows:?1?First of all,this paper uses sodium orthovanadate and thioacetamide as raw materials to synthesize vanadium disulfide by a simple one-step hydrothermal method.The effects of different reaction temperature and time on the physical and chemical properties of VS₂ were investigated to determine the best reaction time and temperature.The experimental results show that VS₂ exhibits good crystallinity,honeycomb like morphology and structure and provides more surface active sites when the reaction time is24 hours and the reaction temperature is 160?.Moreover,the presence of nickel base accelerates the discharge of hydrogen,which makes the electrode material VS₂ show good catalytic ability.?2?Secondly,based on the above results,VS₂ was modified.The hydrogen evolution performance of VS₂ was improved by doping different elements?Co,P,F,Mo?.The results show that compared with the four elements,Mo doping has the best effect on VS₂modification and improves the catalytic performance of VS₂.?3?Finally,based on the first two results,the composite electrode material is further optimized by changing the doping amount of Mo with a single variable method.The results show that when the Mo content is 0.99mmol,VS₂-Mo-0.5 composite electrode material shows the best hydrogen evolution state.When the current density is 100mA cm^-2,the over potential is only 136mV,the smaller Tafel slope is 50mV dec^-1,the larger exchange current density is 1.188mA cm^-2,the smaller load transfer resistance is 0.6?,and the chemical stability is still good after 3000 cycles of test.Mo doping can activate the inert state of active sites on the edge of VS₂ sheet,change the electron cloud density of S atom,increase the number of active sites and increase the conductivity.Compared with VS₂ nano sheet,VS₂-Mo-0.5 composite has a more fluffy structure,which provides a basis for electrode materials to have more specific surface area.