Adsorption Behavior Of The Hydroxyl Radical And Its Effects On The Growth Of MoS₂ Layers

The excessive use of traditional energy has accelerated the deterioration of the global environment and the shortage of global resources.Therefore,the search for new alternative materials has become an urgent problem faced by all mankind.The adjustable band gap and superior stability of MoS2 make it widely used in new electronic and optoelectronic equipment,such as dye-sensitized solar cells,supercapacitors,lithium ion batteries,hydrogen evolution reactions,etc.Although the preparation of MoS2 layers has been widely reported,controllable preparations remain difficult.Based on first-principles density functional theory calculations,we investigated a modified routine using hydroxyl adsorption that recently demonstrated the controlled growth of MoS2 monolayers.The new growth approach impedes the deposition of a second MoS2 layer,however the hydroxyl adsorption and its effects have been mostly unexplored.Through this study,we first explored the adsorption behaviors of the hydroxyl radical(OH)on monolayer MoS2,and briefly discussed its effects on the energetics and electronic structure.Monolayer MoS2 repels charged OH-,whereas the adsorption of the neutral OH radical is energetically favored;the corresponding adsorption energies are 0.09 eV and-1.35eV,respectively.The diffusion barrier of the OH radical on MoS2 is 0.52 eV,indicating that the molecule can quickly diffuse.Next,the study demonstrated that for multiple OH adsorptions,a concerted reaction including OH dissociation and H2O formation is more energetically favored than the adsorption of two OH molecules by 2.50 eV per two OH,which in turn results in a mixed adsorption configuration of O and OH.In addition,we revealed that the OH adsorption creates a mid-gap state and facilitates the reconstruction of the MoS2 edge.