Synthesis Of MoS₂ Nanotubes And MoS₂@C Composites For Electrocatalytic Hydrogen Evolution Reaction

Molybdenum disulfide（MoS₂）is a two-dimensional layered material that has attracted much attention in recent years.Because the structure of MoS₂ is similar to graphene,there are many outstanding performances,and electrocatalytic hydrogen evolution is one of them.As a electrocatalyst that is expected to replace metal platinum,molybdenum disulfide has the advantages of high natural reserves,low cost and high catalytic activity,so it is easy to realize industrial production.However,molybdenum disulfide has many shortcomings,such as easy agglomeration,poor conductivity,which affects its electrocatalytic performance.In this paper,three-dimensional MoS₂ hollow nanotubes were prepared by solvothermal method.This three-dimensional structure can effectively reduce the aggregation of the catalyst,and then expose more active sites.Molybdenum disulfide prepared by solvothermal method usually has poor crystallinity and it will affect catalytic performance.In order to improve the crystallinity of MoS₂ nanotubes,we tested electrocatalytic performance of the samples treated at 600℃,700℃,800℃,900℃ in the inert atmosphere.Then we selected out the best performance（the samples treated by 800℃）.When the current density is 10 mA/cm2,the corresponding overpotential of the samples treated by 800℃ is about 247 mV.Its Tafel slope is about 154 mV/dec.And its stability is also better.Then we used N2/H2 mixture atmosphere to deal with MoS₂ nanotubes.Through H2 to restore S atoms,we can increase material defects to improve the catalytic activity.The experimental results show that the electrocatalytic performance of MoS₂ nanotubes is improved only by continuous heating for more than 6h.However,the shortcomings of this method is that the samples were burned in a high temperature for a long time,so that a large number of samples decreased and the loss rate is high.On the other hand,too long treatment time will reduce the efficiency of the entire process.Finally,we prepared MoS₂ nanotubes as precursors.Then the surface of materials was coated by carbon.It can make MoS₂ nanotubes to increase electrical conductivity by utilizing the excellent conductivity of carbon materials to compensate for its own defects.Finally we chose poly-dopamine as the carbon source.In the experiment,MoS₂@C nanotubes were prepared by the addition of dopamine hydrochloride around the MoS₂ nanotubes,and then polymerizing in the buffer solution.The electrocatalytic performance of MoS₂@C nanotubes was characterized by SEM,XRD and Raman.The results show that when the mass ratio of dopamine hydrochloride and MoS₂ nanotubes is 0.1: 1,the properties of the material are the best,and its starting potential is about-140 mV.When the current density reaches 10 m A/cm2,the potential is about 198 mV.Its resistance between the sample and the electrolyte is about 109.27 Ω.Its stability during the reaction is also better.