Atomically Dispersed p-Block Aluminum-Based Catalysts for Oxygen Reduction Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Main group metals are typically considered catalytically inert for oxygen reduction reactions (ORR) due to delocalized valence orbitals.
• Modifying the local coordination environment of metal centers (M-N_x) is a key strategy to enhance catalytic activity.

Purpose of the Study:

• To report, for the first time, atomically dispersed aluminum (Al) catalysts coordinated with nitrogen (N) and carbon (C) for efficient 4-electron ORR.
• To investigate the role of an axial pyrrolyl N group (N_o) in regulating the electronic structure of Al-N₄ sites for improved ORR performance.

Main Methods:

• Synthesis of atomically dispersed Al catalysts with a specific Al-N₄-N_o moiety.
• Electrochemical characterization of ORR activity, selectivity, and durability.
• In situ Raman spectroscopy to probe reaction kinetics.

Main Results:

• The Al-N₄-N_o catalyst demonstrated excellent ORR activity, selectivity, and durability.
• The axial N_o group modulated the Al center's p-band structure, leading to moderate hybridization and alleviated binding energies for ORR intermediates.
• Rapid ORR kinetics were confirmed by in situ Raman spectroscopy.

Conclusions:

• Atomically dispersed Al catalysts with tailored coordination environments can overcome the inertness of main group metals for ORR.
• Fine-tuning the electronic properties, specifically the p-band structure, is crucial for designing efficient single-atom catalysts.
• This research provides fundamental insights and a design strategy for main-group metal-based single-atom catalysts.