Sublimation Transformation Synthesis of Dual-Atom Fe Catalysts for Efficient Oxygen Reduction Reaction

Area of Science:

• Materials Science
• Catalysis
• Electrochemistry

Background:

• Dual-atom catalysts (DACs) show great promise for catalytic applications.
• Precise control over DAC fabrication is a significant challenge.
• Understanding structure-activity relationships in DACs is crucial for performance optimization.

Purpose of the Study:

• To develop a straightforward synthesis for atomically precise dual-atom iron catalysts (Fe2/NC).
• To investigate the structural characteristics and catalytic performance of the synthesized Fe2/NC.
• To elucidate the effect of the Fe-Fe interatomic distance on catalytic activity.

Main Methods:

• Sublimation transformation synthesis using in situ generated Fe2Cl6(g) dimers.
• Aberration-corrected transmission electron microscopy (TEM) for structural analysis.
• X-ray absorption fine structure (XAFS) spectroscopy for detailed structural characterization.
• Electrochemical testing for oxygen reduction reaction (ORR) performance evaluation.
• Density functional theory (DFT) calculations and microkinetic analysis.

Main Results:

• A novel Fe2/NC catalyst with an extended Fe-Fe distance of 0.3 nm was successfully synthesized.
• The Fe2/NC catalyst exhibited superior ORR performance (0.90 V vs. RHE), outperforming Pt/C and Fe single-atom catalysts.
• DFT calculations confirmed that the extended Fe-Fe distance enhances O2 adsorption and protonation kinetics.
• A shorter Fe-Fe distance (~0.25 nm) resulted in lower catalytic activity.

Conclusions:

• A facile synthesis route for atomically precise DACs was established.
• The Fe-Fe interatomic distance significantly impacts catalytic activity in DACs.
• Optimized Fe-Fe distances are critical for enhancing oxygen reduction reaction efficiency.