Interlayer Electronic Coupling Breaks the *OH Desorption Limitation in Single-Atom Oxygen Reduction Catalysts

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The oxygen reduction reaction (ORR) is crucial for energy conversion technologies.
• Sluggish *OH intermediate desorption is a key kinetic limitation in alkaline ORR, particularly for Fe-based single-atom catalysts (SACs).
• Existing coordination engineering strategies for SACs have not fully resolved the *OH desorption bottleneck, suggesting limitations of planar electronic structures.

Purpose of the Study:

• To investigate the impact of interlayer electronic coupling on the ORR kinetics of Fe SACs.
• To design and synthesize a quasi-3D Fe SAC with enhanced *OH desorption properties.
• To evaluate the performance of the novel catalyst in alkaline ORR and Zn-air batteries.

Main Methods:

• Construction of an interlayer-bonded quasi-3D FeN3P single-atom catalyst (FeN3P-BL@NC) utilizing Fe-P bonds for interlayer electronic pathways.
• Characterization of electronic structure changes, including Fe d-electron redistribution and spin state stabilization.
• Electrochemical evaluation of ORR activity, kinetics, and durability in alkaline media.
• Performance testing of the catalyst in primary and rechargeable Zn-air batteries.

Main Results:

• The interlayer coupling effectively redistributed Fe d-electron density, stabilized a higher-spin Fe state, and weakened Fe-O(H) covalency.
• This led to significantly weakened Fe-O(H) interaction, enabling nearly barrierless *OH desorption (ΔG = 0.026 eV).
• FeN3P-BL@NC exhibited outstanding ORR activity (E(1/2) = 0.956 V vs RHE, j(k) = 82.8 mA cm⁻² at 0.85 V) and excellent durability.
• The catalyst achieved high power density (223 mW cm⁻²) and specific capacity (652 mAh g⁻¹ Zn) in Zn-air batteries, outperforming commercial Pt/C.

Conclusions:

• Interlayer electronic coupling is an effective strategy to overcome the intrinsic *OH desorption limitation in Fe SACs.
• This approach provides an orthogonal design dimension beyond conventional coordination engineering for SACs.
• The developed FeN3P-BL@NC catalyst demonstrates significant potential for advanced energy storage applications like Zn-air batteries.