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Vol. 18 (2026)

Modulation of the Spin State of Atomic Fe-N4 Sites with Interlayer-Adjacent Ir-N4 for Superior ORR Activity

https://doi.org/10.1007/s40820-026-02108-9
Yan Tan
School of Physics Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Aoshuang Li
School of Physics Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Yijie Wang
School of Physics Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Xiucai Jiang
School of Physics Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Yiwen Cheng
School of Physics Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Dongliang Chao
Laboratory of Advanced Materials, Laboratory of Molecular Catalysis and Innovative Materials, Faculty of Chemistry and Materials, Aqueous Battery Center, Shanghai Key, Electron Microscope Center of Fudan University, Fudan University, Shanghai 200433, People’s Republic of China
Yuzhong Zhang
School of Physics Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Chuanwei Cheng
School of Physics Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China

Corresponding Author: Chuanwei Cheng

cwcheng@tongji.edu.cn

Nano-Micro Letters, Vol. 18 (2026), Article Number: 272

Abstract

Development of efficient and durable oxygen reduction reaction (ORR) electrocatalysts is of great interest yet remains challenging. Herein, we predicted and screened a bilayer graphite carbon-supported Ir-N4/Fe-N4 catalyst with high ORR activity using density functional theory calculations. Subsequently, various bimetallic single atom supported on 3D ordered macroporous carbon were rationally designed and experimentally synthesized via a colloidal microsphere template-confined reaction method. As anticipated, the resulting Ir-N4/Fe-N4 bimetallic single-atom catalysts (IrFe-SACs) exhibit superior ORR activity and durability, reaching a half-wave potential of 0.928 V. The IrFe-SACs also demonstrate outstanding performance in Zn-air batteries, including a high discharge power density (314 mW cm⁻2) and excellent cycling stability (~ 1650 cycles over 550 h). Further experimental characterizations and theoretical analysis reveal that introducing interlayer-adjacent Ir-N4 sites facilitates the transition of Fe-N4 from a low-spin state to a medium-spin state, which optimizes the spin polarization of Fe 3d orbitals and enhances the non-localization of the Fe–O/OH molecular orbital, thereby significantly improving the ORR intrinsic activity and durability of atomic Fe-N4 sites.


Highlights:
1 Ir-N4 induce spin polarization and trigger a low-spin to medium-spin transition at Fe centers, enhancing electron delocalization in Fe-O frontier orbitals, optimizes oxygen intermediate adsorption energies.
2 Modulation of spin state of active center optimizes the adsorption energy and enhancing intrinsic catalytic activity (E1/2 = 0.928 V for oxygen reduction reaction).
3 3D ordered macroporous carbon framework ensures high accessibility of atomic sites, resulting in excellent batteries performance, i.e., a discharge power density of 314 mW cm−2, specific capacity of 817.5 mAh g−1.

Keywords

Single-Atom catalysts Spin-State transition Interlayer interactions 3D ordered microporous Zn-Air batteries
Tan, Yan, Aoshuang Li, Yijie Wang, Xiucai Jiang, Yiwen Cheng, Dongliang Chao, Yuzhong Zhang, and Chuanwei Cheng. 2026. “Modulation of the Spin State of Atomic Fe-N4 Sites With Interlayer-Adjacent Ir-N4 for Superior ORR Activity”. Nano-Micro Letters 18 (March):272. https://doi.org/10.1007/s40820-026-02108-9.
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