Understanding catalysis in a multiphasic two-dimensional transition metal dichalcogenide

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Understanding processing-structure-property relationships in monolayer materials is vital for advanced applications.
• Molybdenum disulfide (MoS2) is a promising catalyst for artificial photosynthesis, but its structural and property variations are debated.
• Existing research lacks definitive structural characterization of MoS2 allotropes and their catalytic implications.

Purpose of the Study:

• To unambiguously determine the structure of molybdenum disulfide (MoS2) monolayers.
• To investigate the effect of lithium intercalation on MoS2 structure and properties.
• To evaluate the catalytic activity of modified MoS2 for hydrogen evolution.

Main Methods:

• High-resolution transmission electron microscopy (HRTEM) for structural analysis.
• Density functional theory (DFT) calculations to support experimental findings.
• Electrochemical characterization to assess hydrogen evolution reaction (HER) activity.

Main Results:

• Lithium intercalation induced a phase transformation of MoS2 basal planes from 2H to 1T' (clustered Mo).
• The 1T' phase significantly altered hydrogen adsorption energetics (ΔG(H)), lowering it from +1.6 eV (2H) to +0.18 eV (1T').
• Basal plane activation of 1T'-MoS2 demonstrated high catalytic activity for hydrogen evolution, comparable to state-of-the-art catalysts.

Conclusions:

• The study provides definitive structural insights into MoS2 monolayers and their transformations.
• Lithium intercalation is an effective strategy to tune MoS2 properties for enhanced catalysis.
• Activated 1T'-MoS2 basal planes show great potential for efficient artificial photosynthesis and hydrogen production.