The Investigation On The Catalytic Activity And Tuning For Hydrogen Evolution Reaction In MoS₂ Nanoribbons

Molybdenum disulfide（MoS₂） nanomaterials have been gaining researchers’ widely attention as promising candidates for hydrogen evolution reaction（HER） catalyst Pt. Generally, the effect of edge structure on the catalytic HER activity of MoS₂ nanoribbons is critical. The geometry, electronic properties and catalytic HER activity of MoS₂ nanoribbons can be changed obviously by applying strain, introducing defects etc. Theoretical investigation on the catalytic activity and tuning for HER in MoS₂ nanoribbons has great significance in improving the activity of MoS₂ materials for HER and designing new electrochemical hydrogen evolution catalyst efficiently. Therefore, we present a systematic theoretical investigation on the HER activity in different MoS₂ nanoribbons by using density functional theory in this paper, expecting that our conclusion can bring meaningful theoretical reference for future research on the catalytic activity and tuning for HER in MoS₂ materials.The first chapter mainly introduces the principle of electrochemical hydrogen evolution, as well as the structure, application, preparation and catalytic HER activity of MoS₂ material, and points out the research purpose and significance of this subject. The second chapter briefly describes the basic theory of calculation and Vienna ab-initio Simulation Packages（VASP） used here.In the third chapter, we have studied the impact of the edge structure on the geometry, electronic properties and catalytic HER activity in MoS₂ nanoribbons systematically. The results show that the different binding strengths between theH atom and S atom are caused by the differences in edge structures,demonstrating that edge structures in MoS₂ nanoribbons indeed have a great influence on the catalytic activity of HER. Meanwhile, research indicates that hydrogen adsorption can make nanoribbons exhibiting metal properties. In conclusion, only when H atom binding with adsorption sites is neither strong nor weak, corresponding to gibbs free energy closing to 0 eV, can the catalytic HER activity of MoS₂ nanoribbons achieve the best.In the fourth chapter, we have studied and analyzed the effect of width,stress and defect on geometry and electronic properties in MoS₂ nanoribbons,then we have discussed the turning effect of these factors on HER in MoS₂ nanoribbons. The results show that the stability of Mo S2 nanoribbons is gradually improved with the increasing of the width, but the HER activity changes a little. So we can know the turning effect of width on the HER activity of MoS₂ nanoribbons is not obvious. In addition, the catalytic HER activity of MoS₂ nanoribbons can be improved within a certain compressive stress range,while the tensile stress produces negative effects on the HER activity. When the strain reaches-13%, MoS₂ nanoribbons have the highest HER activity. The presence of vacancy defects can cause atoms re-bonding around the defect, and affect the bond strength between H atom and adsorption sites, ultimately leading to the differences in HER activity in different structures with defects. We find overlap of the electronic states of S atom and H atom near the Fermi level can be beneficial to improve the catalytic HER activity of MoS₂ nanoribbons, when MoS₂ nanoribbons suffer strain and defect.