MoS₂ stacking matters: 3R polytype significantly outperforms 2H MoS₂ for the hydrogen evolution reaction

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Transition metal dichalcogenides (TMDs) are promising materials for electronics and electrocatalysis.
• Molybdenum disulfide (MoS₂) is a notable TMD with significant scientific interest.
• The 3R MoS₂ polytype remains largely unexplored for catalytic applications.

Purpose of the Study:

• To investigate the exfoliation and hydrogen evolution reaction (HER) performance of the 3R MoS₂ polytype.
• To compare the HER activity of 3R MoS₂ with the commonly available 2H MoS₂ polytype.
• To understand the phase conversion mechanisms influencing catalytic activity.

Main Methods:

• High-temperature, high-pressure synthesis of bulk 3R MoS₂.
• Exfoliation of 3R MoS₂ using sodium naphthalenide.
• Benchmarking HER performance against the 2H MoS₂ polytype.
• Analysis of material quality and phase composition.

Main Results:

• The 3R MoS₂ polytype facilitates conversion to the metallic 1T phase more effectively than the 2H polytype.
• Surface oxidation in the 2H polytype hinders conversion to the active 1T phase.
• The 3R MoS₂ polytype achieved a lower overpotential of -0.25 V vs. RHE for HER.
• The 2H MoS₂ polytype exhibited an overpotential of -0.30 V vs. RHE.

Conclusions:

• The 3R MoS₂ polytype is a more suitable precursor for synthesizing highly active MoS₂ catalysts for HER.
• Chemically exfoliated 3R MoS₂ demonstrates enhanced catalytic performance due to increased 1T phase content.
• This study highlights the potential of the 3R polytype in advancing electrocatalysis for hydrogen production.