Study On Hydrothermal Control Growth And Electrochemical Performance Of MoSe₂ Ultrathin Nanosheets

With the increasingly serious environmental crisis and energy shortage,people are increasingly aware that clean and efficient energy plays a key role in the development of society.Hydrogen receives great attention because of its unique advantages.It's common to produce hydrogen from electrocatalytic water splitting.In this way,the study of catalysts in the electrocatalytic hydrogen evolution reaction(HER)is of great significance.At the same time,considering the restrictions on energy use,energy storage devices such as supercapacitors and batteries are also in urgent need of development.Transition metal dichalcogenides(TMDs)stand out for their superior performance in fields like electrocatalysis,photocatalysis and energy storage in recent years.Molybdenum diselenide(MoSe2)as a typical layered TMD is worth investigating.Although these materials are famous for their easy availability and low price,the mediocre conductivity and the limited number of active sites greatly hinder the application of them.Therefore,the microstructure of MoSe2 is adjusted to have better conductivity and expose more active sites,thereby exhibiting better electrocatalytic performance.On the one hand,based on the previous work,the defects of the Mo-rich ultrathin MoSe2 nanosheets were regulated,and the corresponding supercapacitors and electrocatalytic properties were explored.On the other hand,through experimental exploration,a kind of MoSe2 material with thinner morphology and better conductivity has been attained via a different synthesis route.This dissertation consists the following parts:1?We modulated the N-doped MoSe2 through a colloidal synthesis.The product has a feature of monolayer or a few layer,so that it has more active edge sites,and the doping of Nitrogen element makes the material present 1T-2H phase.As the 1T phase is metallic and the 2H phase is semi-conductive,the intrinsic conductivity of the as prepared sample has been changed.This N-MoSe2 shows excellent electrocatalytic performance in HER,the onset overpotential of the N-MoSe2 is 45 mV,and the Tafel slope is as low as 38 mV dec-1.It also presents high durability during the process.This method is easy to operate,and can improve the conductivity and the number of the active sites at the same time,which can give an new insight into the synthesis of more efficient catalysts.2?Exploring the effects of defects on the supercapacitor properties and hydrogen evolution reaction of ultra-thin MoSe2 nanosheets.The edge Se defect of MoSe2 is recognized as the active site of HER,and on the other hand,the carrier transport ability and the specific surface area of the material are the main factors affecting the pseudocapacitance.By studying the relationship between the defects of MoSe2 and its electrocatalytic performance,the factors affecting the performance of MoSe2 supercapacitors and the HER performance corresponding to different defect concentrations were explored.Experiments show that the supercapacitors performance of MoSe2 also increases with the increase of defect concentration,while the defect concentration increases as the temperature increases.The sample prepared at 300 0?achieved an optimum performance of 466.7 F/g in 1 A/g of 3 mol/L KOH.And the HER activity also increases.