Solid-state stepwise temperature-programmable synthesis of bioinspired Fe-N-C oxygen reduction electrocatalyst featuring Fe-N₅ configuration

Wei Sang^{¹^,^§}, Somboon Chaemchuen^{¹^,⁵^,^§}, Longyang Zhang^¹, Zechen Wang^¹, Xingchuan Li^¹, Cocoro Andrew Nagasaka^², Mo Xiong^³, Naoki Ogiwara^², Cheng Chen^{¹^,⁴}, Zhao Wang^⁹, Jian Zhang^¹⁰, Francis Verpoort^{¹^,⁷^,⁸}, Shichun Mu^¹, Zongkui Kou^{¹^,⁴}(), Tingting Wang^⁶()

1State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China

2Department of Basic Science, School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan

3MOE Key Laboratory for Non-Equilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiao tong University, Xi’an 710049, China

4Sanya Science and Education Innovation Park of Wuhan University of Technology, Sanya 572000, China

5Department of Chemical Engineering, Faculty of Engineering, Mahidol University, Nakhon Pathom 73170, Thailand

6School of Mathematical & Physical Sciences, Wuhan Textile University, Wuhan 430200, China

7Joint Institute of Chemical Research (FFMiEN), Peoples Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya Str., 117198 Moscow, Russia

8National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russia

9Hubei Key Laboratory of Ferro, & Piezo-electric Materials and Devices, Faculty of Physics and Electronic Sciences, Hubei University, Wuhan 430062, China

10School of Chemistry and Chemical Engineering, Hainan University, Haikou 57022, China

^§ Wei Sang and Somboon Chaemchuen contributed equally to this work.

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A novel solid-state stepwise temperature-programmable (SST) route was developed to achieve direct, facile and green synthesis of bioinspired Fe-N₅-C catalyst. Fe-N₅-C shows excellent electrocatalytic performance (half-wave potential: 0.92 V, current density: 15.6 mA·cm⁻² at 0.85 V), with Fe sites donating 0.1 e⁻ to the axial N ligand, enhancing O₂ activation and *OH desorption.

Abstract

The bioinspired Fe-N-C features an asymmetric Fe-N₅ configuration to produce active metal-oxygen intermediates by introducing axial N ligand into a symmetric Fe-N₄ structure, enabling highly active oxygen reduction reaction (ORR). However, the artificial creation of active Fe-N₅ configuration with a direct, facile and green method has been rarely developed yet, as current techniques involve complex processes and costly precursors. Herein, we advance a novel solid-state stepwise temperature-programmable (SST) route to directly produce bioinspired Fe-N₅-C. We then demonstrate that such a Fe-N₅-C exhibits a quite higher half-wave potential (0.92 V) with 22-fold faster ORR kinetics (15.6 mA·cm⁻² @ 0.85 V) over that of the commercial Pt/C counterpart. Indeed, we perform density functional theory (DFT) to find that the Fe is discharged with an extra 0.1 e⁻ through the axially coordinate N ligand, which significantly enhances the ability to activate O₂ and enables an easier desorption of the crucial intermediate *OH on the Fe-N₅ configuration over the conventional Fe-N₄ structure.

Keywords

single atom catalysts Fe-N₅ coordination solvent-free synthesis oxygen reduction reaction (ORR)metal-air battery

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References

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Solid-state stepwise temperature-programmable synthesis of bioinspired Fe-N-C oxygen reduction electrocatalyst featuring Fe-N5 configuration