Altering Ligand Fields in Single-Atom Sites through Second-Shell Anion Modulation Boosts the Oxygen Reduction
Jiayi Qin1, Hui Liu1, Peichao Zou1
1Department of Physics and Astronomy, University of California, Irvine, California 92697, United States.
Journal of the American Chemical Society
|January 28, 2022
Summary
This study introduces a sulfur-anion coordination strategy to enhance single-atom ruthenium catalysts on carbon (Ru-N-C) for the oxygen reduction reaction (ORR). The modified Ru-N-C catalyst demonstrates superior activity and durability, outperforming commercial platinum/carbon (Pt/C).
Area of Science:
- Electrocatalysis
- Materials Science
- Nanotechnology
Background:
- Single-atom catalysts (SACs) with metal-N4 moieties on carbon supports (M-N-C) are promising for oxygen reduction reaction (ORR).
- 4d and 5d transition metal (TM4d,5d) M-N-C catalysts offer enhanced durability and resistance to Fenton reactions compared to 3d counterparts.
- Improving the ORR activity of TM4d,5d-N-C catalysts requires precise tuning of the ligand field environments.
Purpose of the Study:
- To develop a strategy for modulating the ligand field of single-atom TM4d,5d sites for improved catalytic properties.
- To investigate the effect of sulfur anion coordination on the structure and ORR performance of single-atom ruthenium-nitrogen-carbon (Ru-N-C) catalysts.
- To evaluate the catalytic activity, durability, and performance in metal-air batteries of the S-anion-coordinated Ru-N-C catalyst.
Main Methods:
- Utilizing single-atom Ru-N-C as a model system.
- Employing a sulfur anion coordination strategy to modify the catalyst's structure.
- Conducting density functional theory (DFT) calculations to understand the electronic structure and reaction mechanisms.
- Fabricating and testing metal-air batteries with the modified catalyst.
Main Results:
- Sulfur anions coordinate with nitrogen atoms in the second shell of Ru centers, effectively tuning the electronic configuration of Ru sites.
- The S-anion-coordinated Ru-N-C catalyst exhibits significant ORR activity and exceptional long-term durability.
- Performance surpasses commercial Pt/C and most reported single-atom catalysts.
- DFT calculations indicate lower adsorption energy of ORR intermediates on Ru sites, explaining the enhanced activity.
- Metal-air batteries demonstrate fast kinetics and excellent stability using the S-anion-coordinated Ru-N-C catalyst.
Conclusions:
- Sulfur anion coordination is an effective strategy for tuning the ligand field and enhancing the ORR performance of single-atom 4d/5d transition metal catalysts.
- The developed S-anion-coordinated Ru-N-C catalyst represents a highly promising alternative to traditional ORR electrocatalysts.
- This approach offers a pathway for designing advanced single-atom catalysts for energy conversion applications.
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