Axial chlorine coordination reconstructs Fe-N₄ electronic structure for efficient pH-universal oxygen reduction...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Single-atom catalysts (SACs) are crucial for energy conversion.
• Existing iron single-atom catalysts (Fe SACs) face challenges like active-site blockage and aggregation.
• Developing stable and highly active Fe SACs is essential for advanced electrochemical applications.

Purpose of the Study:

• To design and synthesize a novel 2D nanosheet catalyst with axial chlorine-coordinated Fe-N4 sites (Fe-N4Cl).
• To investigate the electronic structure modulation and oxygen reduction reaction (ORR) performance of the Fe-N4Cl catalyst.
• To evaluate the catalyst's efficacy in various electrolytes and its application in zinc-air batteries.

Main Methods:

• Molten salt-assisted pyrolysis was employed to create the 2D nanosheet catalysts.
• Electrochemical techniques were used to assess the oxygen reduction reaction (ORR) activity in alkaline, neutral, and acidic media.
• Performance evaluation in zinc-air batteries, including power density and long-term stability tests.

Main Results:

• The Fe-N4Cl catalyst demonstrated enhanced electronic structure due to axial chlorine coordination.
• Superior ORR performance was observed compared to commercial Pt/C, with half-wave potentials of 0.921 V (alkaline), 0.742 V (neutral), and 0.771 V (acidic).
• In Zn-air batteries, the catalyst achieved a peak power density of 176.5 mW cm⁻² and maintained stability for over 720 hours.

Conclusions:

• The developed Fe-N4Cl catalyst effectively addresses the limitations of traditional Fe SACs.
• Axial chlorine coordination is a viable strategy for tuning the electronic properties and enhancing ORR activity.
• The catalyst shows significant promise for next-generation energy conversion devices, particularly zinc-air batteries.