Revealing the failure mechanism and designing protection approach for MoS2 in humid environment by first-principles investigation

The moist circumstance (e.g., O₂ and H₂O molecule) is one of the critical factors affecting the application of MoS₂, which lead to MoS₂ failure. Fortunately, metal-atoms doping MoS₂ is commonly used to decrease damage of MoS₂ by O₂ or H₂O molecule. To understand and explore the microscopic mechanism of MoS₂ failure, the interaction of O₂, H₂O molecule with defect-free, defected MoS₂ is calculated using first-principles method. It could be found that the failure of MoS₂ results mainly from the defects, which make the exposed Mo atoms more active and easy to react with O₂ or H₂O molecule. Therein to, S-vacancy defect of MoS₂ (MoS₂-V_S1 species) is the reaction outset point of O₂ environment, and triple vacancy defect of MoS₂ (MoS₂-V_S2+Mo species) is that of H₂O environment. Based on this failure mechanism, the typical Ti or Pb elementals doped MoS₂ are studied, the calculation results indicate that Ti or Pb doping elements can retard effectively the failure of MoS₂ in humid environment through reacting preferentially with or repulsing to O₂ or H₂O molecules, and even restraining the diffusion of H atom dissociated from H₂O molecule. All of these will be helpful for the design, synthesis, and application of related transition metal dichalcogenides.