Spin engineering of single-site metal catalysts

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Single-site metal atoms (SMAs) on supports offer high atom utilization and catalytic performance.
• Rational design of SMAs with optimized configurations and high activity, particularly considering electron spin, remains a challenge.

Purpose of the Study:

• To rationally design and synthesize configuration-optimized single-site metal atoms (SMAs) with high activity for the oxygen reduction reaction (ORR).
• To investigate the role of electron spin states in the enhanced catalytic activity of SMAs.

Main Methods:

• Synthesis of N-coordinated Fe single atoms distributed over axial carbon micropores to form dangling-FeN4 centers (d-FeN4).
• Electrocatalytic evaluation of d-FeN4 for ORR in HClO4.
• Theoretical calculations and electronic structure characterization to understand the spin states and reaction mechanisms.

Main Results:

• The synthesized d-FeN4 demonstrated significantly higher intrinsic activity for ORR compared to FeN4 without micropores and commercial Pt/C.
• Theoretical and experimental results indicated that d-FeN4 possesses a medium spin state (t2g4 eg1) in the central Fe atom.
• This medium spin state facilitates electron transition, enabling facile formation of singlet oxygen species from triplet oxygen, leading to faster ORR kinetics.

Conclusions:

• The study successfully demonstrates a unique d-FeN4 structure with enhanced ORR activity.
• Electron spin tuning in SMAs is a crucial factor for optimizing catalytic performance.
• This work provides fundamental insights into spin-dependent catalysis for advanced energy applications.