Catalytic Properties Of Mechanically Curved Janus MoSSe

Over the past decades,transition metal sulfides have been shown to be promising catalysts for the hydrogen evolution reaction.Recently,the research team synthesized a new type of TMDs material Janus TMDs in the laboratory,and the asymmetry between atoms may further improve its hydrogen catalytic performance.In this paper,the structural parameters and catalytic activity of hydrogen evolution reaction of two kinds of monolayer Janus MoSSe models,flat and curled,along the Armchair and Zigzag directions are systematically studied based on density functional theory.Specifically,the Gibbs free energies of the original basal plane and the adsorption sites after introducing chalcogen atom defects were calculated.The results show that the pristine Janus MoSSe monolayer nanoribbons are catalytically inert on their basal planes,and the catalytic activity is improved after introducing low concentrations of S\Se defects,which activate the catalytic performance of the basal planes of the nanoribbons.The specific conclusions are as follows:1.Hydrogen catalytic activity of Janus MoSSe nanoribbons:Under the original conditions,the ΔGH of all adsorption sites of the nanoribbons along the Armchair direction is between 1.242eV～2.321eV,and the ΔGH of all adsorption sites of the nanoribbons along the Zigzag direction is between 0.98eV～1.73eV,the Gibbs free energy difference of nanoribbons along the Zigzag direction is closer to zero.After introducing 1.75%S defect or 1.45%Se defect,the ΔGH value of the nanoribbons along the Armchair direction is reduced to between-0.264eV～-0.363eV,and the value of ΔGH of the nanoribbons along the Zigzag direction is reduced to between-0.309eV～-0.516eV,overall,the nanoribbons adsorption sites along the Armchair direction have stronger hydrogen catalytic activity.In particular,among the two nanoribbon models,the curved MoSSe nanoribbons has the most obvious change in hydrogen evolution performance before and after the introduction of defects,and the ΔGH of the curved Janus MoSSe nanoribbon model along the Armchair direction is reduced from 2.321 eV to-0.264eV after introducing Se defects.After calculation,the defect formation energies of all nanoribbon models range from 2.375eV/A to 3.437eV/A,indicating that the formation of these defects is not difficult.2.Janus MXY(M=Mo,W;X,Y=S,Se,Te;X#Y)hydrogen catalytic activity performance:In this paper,the curved conditions of six Janus MXY(M=Mo,W;X,Y=S,Se,Te;X≠Y)under stress-free state are comprehensively studied,the hydrogen catalytic performance and defect formation energy of these Janus structures were calculated systematically when X\Y defects were introduced along the Armchair direction and Zigzag direction.The calculated results show that the Janus MXY nanoribbons along the Armchair direction have stronger hydrogen evolution reactivity on the adsorption sites than the six Janus MXY nanoribbons along the Zigzag direction,And the hydrogen evolution performance of Janus MXY nanoribbons is better when Y defects are introduced than when X defects are introduced.It is worth noting that theΔGH values of Janus WSTe and Janus MoSTe curved nanoribbons along the Armchair direction after introducing Te defects are-0.072eV and 0.097eV,respectively,showing excellent hydrogen catalytic activity.In these two Janus nanoribbons,the formation energies of Te defects are 1.875eV/A and 1.876eV/A,respectively,and the defects are relatively easy to form.