Precisely Control Relationship between Sulfur Vacancy and H Absorption for Boosting Hydrogen Evolution Reaction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Effective catalysts are crucial for efficient water splitting and hydrogen production.
• Nickel disulfide (NiS2) is a promising material for electrocatalytic applications.
• Controlling material properties is key to enhancing catalytic activity.

Purpose of the Study:

• To enhance the electrocatalytic performance of NiS2 for the hydrogen evolution reaction (HER).
• To investigate the effect of sulfur vacancies (Vs) on NiS2's catalytic properties.
• To establish a simple method for improving catalyst activity.

Main Methods:

• Anionic etching was employed to tailor the concentration of sulfur vacancies (Vs) in NiS2.
• Electrocatalytic performance for HER was evaluated in 1 M KOH.
• In situ attenuated-total-reflection Fourier transform infrared spectroscopy (ATR-FTIRS) monitored intermediate adsorption.
• Density functional theory (DFT) calculations were performed to understand hydrogen adsorption.

Main Results:

• NiS2-Vs with 5.9% sulfur vacancies exhibited an ultralow onset potential of 68 mV.
• The optimized catalyst demonstrated long-term stability for 100 hours.
• ATR-FTIRS showed favorable S-H* peak appearance at low voltage, indicating efficient HER.
• DFT calculations confirmed optimal hydrogen adsorption energy (|ΔGH*| = 0.17 eV) for NiS2-Vs 5.9%.

Conclusions:

• Anionic etching provides a facile route to precisely control sulfur vacancies in NiS2.
• Optimized sulfur vacancy concentration in NiS2 significantly enhances HER activity and stability in alkaline media.
• This vacancy engineering strategy offers a promising pathway for developing advanced electrocatalysts.