Engineering Vacancies at the 2D Nanocrystals for Robust Bifunctional Electrocatalysts

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Water splitting for green energy production relies on efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
• Non-noble metal catalysts are sought as sustainable alternatives to precious metals for these reactions.

Purpose of the Study:

• To develop a facile method for synthesizing defect-rich non-noble metal nanosheets for bifunctional electrocatalysis.
• To investigate the role of sulfur vacancies in enhancing the catalytic activity of transition-metal dichalcogenides (TMDs) for HER and OER.

Main Methods:

• A two-step electrochemical synthesis at room temperature was employed to create defect-rich nanosheets.
• First-principle calculations were utilized to elucidate the catalytic mechanism and the effect of sulfur vacancies.
• Electrochemical characterizations (Tafel slope, overpotential) were performed in acidic and alkaline media.

Main Results:

• First-principle calculations predicted that sulfur vacancies promote electron transfer and lower the energy barrier for electrocatalysis.
• Defect-rich atomic-thick tantalum sulfide demonstrated excellent bifunctional catalytic activity for both HER and OER.
• The catalyst exhibited low overpotentials (0.099 V for HER, 0.153 V for OER) and favorable Tafel slopes (39 mV/dec for HER, 38 mV/dec for OER).
• High stability was observed in both acidic and alkaline solutions.

Conclusions:

• The synthesized defect-rich tantalum sulfide nanosheets are effective dual-function electrocatalysts for water splitting.
• Defect engineering, specifically sulfur vacancies, significantly enhances catalytic performance.
• These materials hold promise for large-scale, cost-effective hydrogen and oxygen production.