Deciphering Local Microstrain-Induced Optimization of Asymmetric Fe Single Atomic Sites for Efficient Oxygen...

Area of Science:

• Materials Science
• Catalysis
• Electrochemistry

Background:

• Symmetric electron distribution in porphyrin-like Fe single-atom catalysts limits intrinsic activity.
• Geometric microstrain is a key factor for optimizing catalyst performance.
• Asymmetric catalysts offer potential for enhanced catalytic properties.

Purpose of the Study:

• To investigate the role of local microstrain in boosting the intrinsic activity and durability of asymmetric Fe-N3S1 single-atom catalysts.
• To understand how geometric configurations influence catalytic performance.
• To explore dynamic changes in catalyst structure during operation.

Main Methods:

• Synthesis of asymmetric Fe-N3S1 single-atom catalysts on hollow carbon nanosphere substrates.
• Introduction of controlled compressive and tensile strains via substrate curvature.
• Electrochemical characterization including half-wave potential and turnover frequency measurements.
• Operando spectroscopy to monitor dynamic structural changes.

Main Results:

• Curved hollow carbon nanosphere substrate induces significant local strain on Fe-N and Fe-S bonds.
• Strained Fe-N3S1 sites exhibit downshifted d-band centers, accelerating *OH reduction kinetics.
• FeNS-HNS-20 demonstrates high half-wave potential (0.922 V vs. RHE) and turnover frequency (6.2 s-1 site-1), outperforming flat counterparts.
• Operando spectroscopy reveals dynamic optimization of Fe-N3S1 to Fe-N3 sites, mitigating *OH intermediate overadsorption.

Conclusions:

• Local microstrain is crucial for enhancing the intrinsic activity and durability of asymmetric Fe-N3S1 catalysts.
• Geometric configuration of the substrate plays a vital role in tuning catalyst performance.
• Dynamic structural evolution under operating conditions contributes to improved catalytic efficiency.
• This study provides a pathway for designing advanced asymmetric single-atom catalysts through precise geometric control.