Electronically and Geometrically Modified Single-Atom Fe Sites by Adjacent Fe Nanoparticles for Enhanced Oxygen...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Iron-Nitrogen-Carbon (Fe-N-C) materials are leading alternatives to platinum catalysts for the oxygen reduction reaction (ORR).
• Understanding the specific structural features that contribute to the high ORR activity of Fe-N-C materials remains a challenge.

Purpose of the Study:

• To investigate the relationship between the electronic and geometric structures of isolated Fe-N-C sites and their ORR performance.
• To elucidate how secondary thermal activation temperature influences these structures in Fe single-atom catalysts (SACs) supported on nitrogen-doped carbon (NC).

Main Methods:

• Fabrication of NC-supported Fe SACs with varying secondary thermal activation temperatures.
• Systematic analysis of electronic and geometric structures.
• Theoretical calculations to assess ORR energy barriers.

Main Results:

• Coordinated atoms and metallic Fe nanoparticles (NPs) significantly alter the electronic structure of isolated Fe-N-C sites.
• Interaction between Fe-N-C sites and Fe NPs modifies the geometric structure of the Fe-N-C sites.
• Optimal electronic and geometric structures, achieved through the co-existence of Fe NPs, reduce rate-limiting energy barriers for ORR.

Conclusions:

• The study provides fundamental insights into the structure-activity relationship governing Fe-N-C catalysts for ORR.
• The findings offer guidance for designing highly efficient Fe-N-C catalysts by controlling the interplay between isolated sites and Fe NPs.