Inter-site structural heterogeneity induction of single atom Fe catalysts for robust oxygen reduction

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Metal-nitrogen-carbon catalysts with hierarchical porosity are promising for oxygen reduction reactions (ORR).
• Understanding the role of structural heterogeneity and individual/interacting sites in catalytic performance remains challenging.

Purpose of the Study:

• To prepare and characterize an efficient hierarchically porous Fe single atom catalyst (Fe SAs-HP).
• To elucidate the structure-activity relationship governing the enhanced ORR performance.

Main Methods:

• Synthesis of hierarchically porous Fe single atom catalyst (Fe SAs-HP).
• Electrochemical testing for ORR performance evaluation (half-wave potential, turnover frequency).
• Theoretical simulations (e.g., DFT) and multilevel operando characterization.

Main Results:

• Fe SAs-HP demonstrated robust ORR performance with a half-wave potential of 0.94 V.
• Mesoporous Fe-N4 sites, regulated by microporous sites, act as active centers facilitating O2 activation and *OH desorption.
• Operando characterization revealed dynamic evolution of Fe sites from Fe-N4 to Fe-N3 under working conditions.

Conclusions:

• Structural heterogeneity in Fe SAs-HP is key to optimizing ORR activity.
• The interplay between micropores and mesopores enhances electron regulation and catalytic efficiency.
• Understanding site evolution under working conditions provides insights into designing advanced ORR electrocatalysts.