Hydrogen Catalytic Properties Of 1S Phase Two-dimensional Transition Metal Chalcogenides

Two-dimensional transition metal chalcogenides(TMDs),as an effective non-noble metal catalyst of hydrogen evolution reaction(HER),have attracted much attention.Based on the first-principles calculation method of density functional theory(DFT),the hydrogen catalytic properties of two-dimensional 1S phase MoSSe monolayers(1S-MoSSe)were systematically studied by calculating the catalytic activity of original substrate,the contributions of vacancy for the enhancement of substrate catalytic activity and the effect of biaxial strain on the catalytic activity.The spin polarization effect is considered in the simulation,and the DFT-D3 correction is used to avoid the influence of van der Waals force.The stability of two-dimensional 1S-MoSSe structure is proved by calculating the phonon spectrum.The calculated hydrogen adsorption energy of each site on the inert substrate is in range from 0.52eV to 2.67eV,which shows that the chalcogenide substrate can not effectively adsorb hydrogen;the introduction of defects significantly enhances the hydrogen catalytic activity of the chalcogenide substrate of the two-dimensional 1S-MoSSe.Due to the atomic asymmetry of Janus structure,ΔGH of 1S-MoSSe monolayer are-53 and-28 meV for S-and Se-vacancy defect,respectively.Two-dimensional 1S-MoSSe can obtain a ΔGH close to 0 with free strain.This shows that the hydrogen catalytic activity of two-dimensional Janus TMDs is better than that of MoS2.We attribute it to the destruction of out of plane symmetry by the unique Janus configuration of two-dimensional MoSSe.Its non stacking structure makes it naturally have a certain degree of bending strain.Furthermore,the effect of biaxial strain on the hydrogen catalytic activity of two-dimensional 1S-MoSSe defect structure was studied.The results show that in the range of-2%to+2%biaxial strain,the hydrogen catalytic activity of two-dimensional 1S-MoSSe defect structure shows a correlation with the strain,showing a decrease ΔGH for tensile strain while he compression strain increases ΔGH.It is worth noting that the catalytic activity of the two-dimensional 1S-MoSSe Se-vacancy defect structure is throughout the catalytic window of ± 50 MeV in the range of ± 2%strain,which indicates that its catalytic performance has a certain anti-strain ability.In addition,we have also studied the hydrogen catalytic properties of two-dimensional 2H phase MoSO(2H MoSO),and the ΔGH of sulfur and oxygen defect states-0.043eV and 0.065eV,respectively,which also showed considerable catalytic activity for the defect state hydrogen.By systematically studying the hydrogen catalytic properties of two-dimensional 1S-MoSSe and 2H-MoSO,we found that two-dimensional 1S-MoSSe and 2H-MoSO all showed excellent hydrogen catalytic performance.