Axial Chlorine Induced Electron Delocalization in Atomically Dispersed FeN4 Electrocatalyst for Oxygen Reduction Reaction with Improved Hydrogen Peroxide Tolerance

Palani Sabhapathy; Puttikam Raghunath; Amr Sabbah; Indrajit Shown; Khasim Saheb Bayikadi; Rui-Kun Xie; Vimal Krishnamoorthy; Ming-Chang Lin; Kuei-Hsien Chen; Li-Chyong Chen

doi:10.1002/smll.202303598

Axial Chlorine Induced Electron Delocalization in Atomically Dispersed FeN4 Electrocatalyst for Oxygen Reduction Reaction with Improved Hydrogen Peroxide Tolerance

Small. 2023 Nov;19(45):e2303598. doi: 10.1002/smll.202303598. Epub 2023 Jul 11.

Authors

Palani Sabhapathy¹, Puttikam Raghunath², Amr Sabbah^{1

3

4}, Indrajit Shown⁵, Khasim Saheb Bayikadi³, Rui-Kun Xie⁶, Vimal Krishnamoorthy⁷, Ming-Chang Lin², Kuei-Hsien Chen^{1

3}, Li-Chyong Chen^{1

8

9}

Affiliations

¹ Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan.
² Department of Applied Chemistry, National Yang-Ming Chiao-Tung University, Hsinchu, 30010, Taiwan.
³ Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan.
⁴ Tabbin Institute for Metallurgical Studies, Tabbin, Helwan 109, Cairo, 11421, Egypt.
⁵ Department of Chemistry, Hindustan Institute of Technology and Sciences, Chennai, 603103, India.
⁶ National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan.
⁷ Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 10607, Taiwan.
⁸ Center of Atomic Initiative for New Materials, National Taiwan University, Taipei, 10617, Taiwan.
⁹ Department of Physics, National Taiwan University, Taipei, 10617, Taiwan.

PMID: 37434392
DOI: 10.1002/smll.202303598

Abstract

Atomically dispersed iron sites on nitrogen-doped carbon (Fe-NC) are the most active Pt-group-metal-free catalysts for oxygen reduction reaction (ORR). However, due to oxidative corrosion and the Fenton reaction, Fe-NC catalysts are insufficiently active and stable. Herein, w e demonstrated that the axial Cl-modified Fe-NC (Cl-Fe-NC) electrocatalyst is active and stable for the ORR in acidic conditions with high H₂ O₂ tolerance. The Cl-Fe-NC exhibits excellent ORR activity, with a high half-wave potential (E_1/2 ) of 0.82 V versus a reversible hydrogen electrode (RHE), comparable to Pt/C (E_1/2 = 0.85 V versus RHE) and better than Fe-NC (E_1/2 = 0.79 V versus RHE). X-ray absorption spectroscopy analysis confirms that chlorine is axially integrated into the FeN4. More interestingly, compared to Fe-NC, the Fenton reaction is markedly suppressed in Cl-Fe-NC. In situ electrochemical impedance spectroscopy reveals that Cl-Fe-NC provides efficient electron transfer and faster reaction kinetics than Fe-NC. Density functional theory calculations reveal that incorporating Cl into FeN4 can drive the electron density delocalization of the FeN4 site, leading to a moderate adsorption free energy of OH* (∆G_OH* ), d-band center, and a high onset potential, and promotes the direct four-electron-transfer ORR with weak H₂ O₂ binding ability compared to Cl-free FeN4, indicating superior intrinsic ORR activity.

Keywords: Cl coordination; FeN4; Fenton reaction; d-band center; electron density; oxygen reduction reaction.

Abstract

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