Size effects and odd-even effects in MoS₂ nanosheets: first-principles studies

Area of Science:

• Materials Science
• Catalysis
• Surface Chemistry

Background:

• Molybdenum disulfide (MoS₂) nanostructures are key catalysts in petroleum hydrodesulfurization.
• Sulfur vacancies are critical for MoS₂ catalytic activity.
• Understanding vacancy formation is essential for optimizing catalysts.

Purpose of the Study:

• Investigate size and odd-even effects on sulfur vacancy formation in MoS₂ nanosheets.
• Determine the energetic favorability of different edge terminations.
• Analyze the impact of vacancy location on formation energy.

Main Methods:

• First-principles calculations were employed to model MoS₂ nanosheets.
• Four types of edge structures were analyzed.
• Energetics of sulfur dimer vacancies (V_S@Cen and V_S@Cnr) were calculated.

Main Results:

• S-terminated edges are energetically more favorable than Mo-terminated edges.
• A significant odd-even effect on sulfur dimer vacancy formation was observed, especially in small nanosheets.
• V_S@Cen vacancies have low formation energy for even-sized nanosheets and high for odd-sized.
• V_S@Cnr vacancies show the opposite trend.

Conclusions:

• MoS₂ nanosheet size dictates sulfur vacancy formation energetics.
• Odd-even effects in vacancy formation lead to unique catalytic properties.
• These findings suggest tailored MoS₂ nanostructures for enhanced hydrodesulfurization.