Research On The Regulation Of Defects And Strains On The Electrochemical Catalytic Properties Of Two-Dimensional Materials

Energy has always been a pillar of human development.With the development of society,the demand for energy is constantly increasing.Due to the limited reserves of traditional fossil fuels and environmental pollution during use,it is extremely urgent to find and develop green,efficient and renewable clean energy.Hydrogen favored by researchers all over the world due to the outstanding properties such as high specific energy per mass,easy storage and transportation,and ability to reduce harmful emissions.The electrochemical hydrogen evolution reaction?HER?is an economical method for the continuous production of hydrogen.Electrochemical catalysts with high conversion efficiencies are key to the hydrogen evolution reaction.At present,the most effective catalysts for the production of hydrogen by electrocatalysis are precious metals such as platinum,rhodium,ruthenium,etc.,but due to the high price and small reserves of these materials,they have hindered from commercial large-scale applications.Finding new and efficient electrochemical catalysts is the core and key to electrochemical hydrogen production.In recent years,graphene-like two-dimensional materials have shown great potential in hydrogen evolution reaction as catalysts due to their unique crystal structure and physicochemical properties.However,the active sites of such materials are mainly located at their few edges,and the large base surface is catalytically inert.In order to enhance the electrochemical catalytic activity of two-dimensional materials,the first-principles calculation method be used to regulate the electrochemical properties of two-dimensional materials through doping,defects and strain.The main results are as follows:1.We studied the catalytic behavior of the grain boundaries?GBs?in monolayer MoS₂ by density functional theory.The calculation results show that the Gibbs free energy??G_H?of hydrogen adsorbed at the grain boundary is about 0.01 eV,which is close to the optimal condition of 0 eV,indicating that the existence of grain boundaries can stimulate the catalytic activity of the base surface in the hydrogen evolution reaction.The S vacancy,the bridge site of the Mo-Mo dimer,and the top site of the S atom of the S-S dimer are the catalytically active sites.Electronic property analysis indicated that the enhanced catalytic activity caused by an increase in the density of states near the Fermi level.2.The effects of strain on the electronic properties and catalytic activity of monolayer SnSe_2?1-x?S_2x?x=0¹?alloys were investigated by density functional theory.The results showed SnSe_2?1-x?S_2x alloys with continuously changing bandgaps from 0.8eV for SnSe₂?x=0?to 1.59 eV for SnS₂?x=1?.The electronic properties of monolayer SnSe_2?1-x?S_2x alloys can be further tuned by applied strain.SnSeS and SnSe_0.5S_1.5monolayers showed the best catalytic activity for HER at a strain of 10%.3.Based on density functional theory,we calculated the catalytic properties of MoS₂by Ni doping.It is found that the formation energies?E_f?values are 5.30 eV,1.83 eV and2.83 eV for the substitution of Ni for Mo at the basal plane,the Mo-edge and the S-edge,respectively,indicating the less possibility of that the substitution of Mo with Ni.Doped Ni atoms easily adsorbed on the S edge of MoS₂.After Ni atoms adsorbed at the edge of S,the Gibbs free energy of hydrogen adsorption is 0.1 eV,indicating that the introduction of single Ni significantly improves the catalytic activity of S-edge.