Charge transfer and vacancy engineering of Fe

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Scalable and renewable ammonia (NH3) synthesis is crucial but hindered by low efficiency and selectivity in nitrogen reduction reaction (NRR) electrocatalysts.
• Existing electrocatalysts often struggle to meet the demands for industrial applications.

Purpose of the Study:

• To develop highly selective and durable electrocatalysts for the nitrogen reduction reaction (NRR) under ambient conditions.
• To innovate technology for overcoming the limitations of current NRR catalysts.

Main Methods:

• Preparation of a core-shell nanostructure: coating polypyrrole (PPy) onto sulfur-doped iron oxide nanoparticles (S-Fe2O3@PPy).
• Characterization of the S-Fe2O3@PPy catalyst's properties and performance in NRR.
• Utilizing density functional theory (DFT) calculations to understand the catalytic mechanism.

Main Results:

• The S-Fe2O3@PPy catalyst achieved a high ammonia production rate of 22.1 μg h⁻¹ mgcat⁻¹.
• A very high Faradic efficiency of 24.6% was obtained, surpassing other Fe2O3-based NRR catalysts.
• Sulfur doping and PPy coating enhanced charge transfer and created oxygen vacancies, serving as active sites.

Conclusions:

• The S-Fe2O3@PPy core-shell nanostructure is a highly selective and durable electrocatalyst for NRR.
• The catalyst's performance is attributed to improved charge transfer, abundant active sites, and optimized N2 activation.
• DFT calculations confirm the S-coordinated iron site's role in activating N2 and lowering the energy barrier for reduction.