Microelectrocatalytic Investigation Of Molybdenum Disulphide Based On Strain Modulation

The growing demand for energy at a societal level and the need to protect the environment have created an urgent need for an energy system based on renewable energy sources.H₂,with its high energy density,is a promising source of clean energy.Electrochemical water splitting is an effective means for clean and efficient hydrogen production.Electrocatalysts can increase the rate and efficiency of chemical conversion and play a vital role in the production of clean energy.Therefore,it is significant to find a catalyst that can replace precious metals.As a representative of two-dimensional transition metal dichalcogenides（TMDs）,molybdenum disulfide（Mo S₂）possesses tunable band gap,unique layered structure and excellent catalytic activity,making it an ideal system for hydrogen evolution catalysis research.However,when used as a catalyst,Mo S₂ also suffers from limitations such as inert basal plane and poor electrical conductivity.As an effective means to tune the band structure and electrical properties of TMDs,strain can affect the density of states（DOS）by causing changes in bond lengths.It is an efficient method to donate electrons to the active sites of catalysts.On the basis of this,we constructed a microelectrocatalytic exploration platform based on Mo S₂ on a strained array substrate.The aim is to improve the catalytic activity of hydrogen evolution on Mo S₂ inert basal plane through strain,and to explore electrochemical processes more precisely with the aid of micro and nano processing techniques.The work covers the following main aspects.（1）Monolayer Mo S₂ was prepared by chemical vapor deposition（CVD）method.The success rate of monolayer Mo S₂ transfer was promoted by improving the application of PMMA-assisted wet transfer on wrinkled substrates,resulting in tighter adhesion of Mo S₂ to the target substrate for strain transfer.（2）By means of Raman,PL and its mapping images,it is confirmed that the strain type is tensile strain.The redshift of the E₂¹ _g peak on the Raman spectrum,the redshift of the peak on the PL spectrum and the decrease in band gap correspond to the d-divergence due to structural changes in Mo S₂ and the hybridisation of the Mo 4d-S 3p orbital,thus causing a redshift in exciton resonance energy.The KPFM characterisation demonstrates a change in the Fermi energy level in the strain region.The movement of electrons triggered the generation of back-to-back built-in electric fields.And the increase in surface charge laid the basis for the interpretation of the enhanced hydrogen evolution properties.（3）Field-effect transistor electrical devices and microelectrocatalytic devices were constructed by photolithography and thermal vapour deposition,which were characterised with the aid of a probe stage and electrochemical workstation.The results show that strain induces changes in carrier transport properties and that the magnitude of the carrier mobility（μ）is altered by strain.But Mo S₂ remains the properties of an n-type semiconductor.The microelectrocatalytic test of selective exposure of the strained region shows that the hydrogen evolution catalytic performance of Mo S₂ is also improved with the introduction of strain,and the hydrogen evolution performance is further improved with the increase of strain.This is due to the strain-induced changes in the density of states（DOS）near the Fermi energy level,which promotes the adsorption of hydrogen atoms and thus enhances the catalytic performance of hydrogen evolution reaction.