Creating Asymmetric Fe-N₃C-N Sites in Single-Atom Catalysts Boosts Catalytic Performance for Oxygen Reduction...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Optimizing single-atom catalysts (SACs) for oxygen reduction reaction (ORR) is crucial for energy technologies.
• Tuning the metal site coordination environment is key to enhancing SAC catalytic activity.

Purpose of the Study:

• To design and synthesize a novel SAC with an asymmetric Fe-N3C-N coordination site.
• To investigate the ORR performance of the new SAC and its application in zinc-air batteries.

Main Methods:

• Synthesis of the Fe-N3C-N SAC via pyrolysis of iron isoporphyrin on polyvinylimidazole (PVI) coated carbon black.
• Electrochemical evaluation of the catalyst's ORR activity in 0.1 M KOH.
• Fabrication and testing of zinc-air batteries using the synthesized catalyst.
• Density functional theory (DFT) calculations to elucidate the catalytic mechanism.

Main Results:

• The C@PVI-(NCTPP)Fe-800 catalyst demonstrated superior ORR activity (E1/2 = 0.89 V vs RHE) compared to Fe-N4-N SACs.
• Zinc-air batteries with this catalyst achieved a high open-circuit voltage (1.45 V) and peak power density (130 mW/cm2), exceeding commercial Pt/C.
• DFT calculations indicated that the asymmetric Fe-N3C-N structure enhances electron donation and facilitates O2 adsorption and activation.

Conclusions:

• The asymmetric Fe-N3C-N active site architecture is an effective strategy for designing high-performance SACs.
• This approach significantly enhances catalytic efficiency for the ORR.
• The developed SAC shows great promise for advanced energy-conversion technologies.