Is Single Layer MoS₂ Stable in the Air?

Area of Science:

• Materials Science
• Surface Chemistry
• Computational Chemistry

Background:

• Molybdenum disulfide (MoS₂) is a promising material for catalysis and electronics.
• Recent experiments suggest MoS₂ monolayers lack long-term air stability, challenging prior assumptions.

Purpose of the Study:

• To investigate the oxidation mechanisms of MoS₂ monolayers using computational methods.
• To understand the factors contributing to the observed instability of MoS₂ in ambient conditions.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• The energetic barriers for oxygen dissociation and subsequent reactions on MoS₂ surfaces were analyzed.

Main Results:

• Exposed Mo-edges of MoS₂ monolayers exhibit low energy barriers for oxygen molecule dissociation.
• Oxidation leads to sulfur atom replacement by oxygen and formation of molybdenum trioxide (MoO₃)-like structures.
• Lattice mismatch between MoS₂ and MoO₃ can induce stress and cracking.

Conclusions:

• Single-layer MoS₂ is susceptible to oxidation, particularly at edge sites.
• The formation of MoO₃ structures facilitates further oxidation and can explain experimental observations of material degradation.