Janus Monolayer Transition-Metal Dichalcogenides.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Chemistry

Background:

• Molybdenum diselenide (MoSe2) is a 2D material with potential applications.
• Janus materials offer unique properties due to broken inversion symmetry.
• Controlled synthesis of novel 2D heterostructures is crucial for advanced functionalities.

Purpose of the Study:

• To synthesize and characterize a novel Janus S-Mo-Se (SMoSe) monolayer.
• To investigate the structural, vibrational, and electronic properties of Janus SMoSe.
• To explore the potential of Janus SMoSe for catalytic applications, specifically the hydrogen evolution reaction (HER).

Main Methods:

• Controlled sulfurization of monolayer MoSe2 to create the Janus SMoSe structure.
• Structural and compositional characterization using Raman spectroscopy, photoluminescence, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS).
• Confirmation of elemental composition and distribution via time-of-flight secondary ion mass spectrometry (ToF-SIMS).
• Density functional theory (DFT) calculations to analyze vibrational modes, electronic band structure, and catalytic mechanisms.

Main Results:

• Successful synthesis of the Janus SMoSe monolayer with distinct S-Mo-Se configuration.
• Experimental characterization confirmed the unique structure and composition.
• DFT calculations showed good agreement with experimental findings for Raman spectra and electronic properties.
• The Janus SMoSe monolayer demonstrated high catalytic activity for the hydrogen evolution reaction on its basal plane.

Conclusions:

• The synthesized Janus SMoSe monolayer is a stable and promising 2D material.
• The observed high HER activity is attributed to the synergistic effects of intrinsic defects and structural strain within the Janus configuration.
• Janus SMoSe presents a new platform for designing efficient electrocatalysts for hydrogen production.