Morphology and atomic-scale structure of single-layer WS2 nanoclusters.

Area of Science:

• Materials Science
• Surface Science
• Catalysis

Background:

• Two-dimensional transition metal sulfides, like molybdenum disulfide (MoS2) and tungsten disulfide (WS2), possess unique electronic and optical properties in their single-layer form.
• Single-layer MoS2 and WS2 are commercially used as hydrotreating and hydrocracking catalysts, making their structural characterization vital for understanding catalytic activity.
• Despite MoS2's prevalence, fundamental properties of single-layer WS2 remain less understood.

Purpose of the Study:

• To elucidate the equilibrium morphology and prevalent edge structures of single-layer WS2 nanoparticles.
• To provide insights into the catalytic role of WS2 edges by understanding their coordination chemistry.

Main Methods:

• Atom-resolved Scanning Tunneling Microscopy (STM) was employed to study Au(111)-supported WS2 nanoparticles.
• Density Functional Theory (DFT) calculations were used to determine edge structures and construct phase diagrams.

Main Results:

• STM revealed that single-layer WS2 sheets form triangular shapes with fully sulfided edges under synthesis conditions.
• The predominant edge structure identified was the (101̅0) W-edge, with the (1̅010) S-edge becoming significant for smaller clusters.
• DFT calculations provided phase diagrams for WS2 edges, detailing sulfur and hydrogen coordination.

Conclusions:

• The study reveals the equilibrium shape and dominant edge structures of single-layer WS2 nanoparticles.
• Understanding these structures and their coordination chemistry is essential for optimizing WS2's catalytic performance.