Sulfur-deficient edges as active sites for hydrogen evolution on MoS₂

Area of Science:

• Computational materials science
• Electrochemistry
• Catalysis

Background:

• The hydrogen evolution reaction (HER) is crucial for sustainable hydrogen production.
• Molybdenum disulfide (MoS₂) is a promising catalyst for HER, but its intrinsic activity varies significantly with site type.
• Understanding the voltage-dependent kinetics and activation energies at different MoS₂ sites is essential for catalyst optimization.

Purpose of the Study:

• To calculate voltage-dependent activation energies for HER on intrinsic MoS₂ sites.
• To estimate HER kinetics on MoS₂ edges with varying sulfur coverage and basal plane S-vacancies.
• To correlate theoretical overpotentials with experimental findings and guide catalyst design.

Main Methods:

• Employed a grand-canonical approach to compute activation energies and reaction kinetics.
• Investigated HER on MoS₂ edges (varying S-coverage) and basal plane S-vacancies.
• Utilized kinetic modeling based on voltage-dependent reaction energetics.

Main Results:

• S-deficient Mo-terminated edges exhibit significantly higher HER activity, with activation energy below 0.5 eV at 0 V vs. SHE.
• Mo-rich sites are crucial for efficient HER; S-rich sites show high energy barriers (>1.5 eV).
• Theoretical overpotentials align with experimental values, decreasing with increased sulfur deficiency and reduced Mo-coordination.

Conclusions:

• MoS₂ catalyst design should focus on exposing and modifying Molybdenum sites for enhanced HER.
• Sulfur deficiency and reduced Molybdenum coordination are key factors in lowering overpotential.
• The study provides fundamental insights into the distinct performance of Mo-rich versus S-rich sites in transition metal dichalcogenides.