Bifunctional Oxygen Electrocatalytic Performance of Atomically Dispersed Fe Anchored on N-doped Graphene

doi:10.15541/jim20250519

Abstract

Abstract:

With the growing demand for efficient and environmental-friendly energy storage systems, zinc-air batteries have emerged as highly promising energy storage devices due to their high energy density, low cost, and environmental friendliness. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which suffer from sluggish kinetics, are critical factors limiting battery performance. Therefore, the development of high-performance and low-cost bifunctional oxygen electrocatalysts is of great significance. In this work, Fe single atoms/clusters anchored graphene hybrid catalysts (Fe-N/Gra) were prepared via a ball-milling assisted pyrolysis method. A series of Fe-N/Gra catalysts were obtained by adjusting the mass ratio of the metal phthalocyanine precursor to graphene, and their bifunctional oxygen electrocatalytic performances were systematically investigated. The results demonstrate that the loading amount of different metal phthalocyanine precursors exerts a significant influence on the catalytic performance of the catalysts. When the loading amount of iron phthalocyanine was 0.02 g, the resulting Fe-N/Gra-0.02 catalyst exhibited the optimal bifunctional catalytic activity for ORR and OER. The ORR half-wave potential reached as high as 0.911 V, and the OER overpotential was 610 mV at a current density of 10 mA·cm^-2. The rechargeable zinc-air batteries assembled with this catalyst as the air electrode achieved a maximum power density of 315 mW·cm^-2 and could sustain stable discharge for 210 h at 10 mA·cm^-2. The excellent bifunctional oxygen catalytic activity of Fe-N/Gra-0.02 is mainly attributed to the atomically dispersed Fe-N_x active sites and the high electrical conductivity of graphene support. In addition, the agglomeration of active sites in the catalysts with excessive loading amounts is detrimental to the manifestation of their high-efficiency catalytic activity. This work provides an experimental basis for the controllable preparation of high-performance non-noble metal bifunctional oxygen catalysts and their practical applications in rechargeable zinc-air batteries.

Key words: iron-anchored nitrogen-doped graphene, single-atom/cluster, oxygen reduction reaction, oxygen evolution reaction, Zn-air battery

CLC Number:

TB383

WANG Jiahui, LIU Jingjing, QIU Yi, WANG Yongxia, CUI Xiangzhi. Bifunctional Oxygen Electrocatalytic Performance of Atomically Dispersed Fe Anchored on N-doped Graphene[J]. Journal of Inorganic Materials, 2026, 41(6): 814-822.

Figures/Tables 5

Fig. 1 Schematic diagram of the preparation process for Fe-N/Gra catalysts

Fig. 2 Physical characterization of the synthesized Fe-N/Gra catalysts (a) TEM image of Fe-N/Gra-0.02; (b) AC-TEM image of Fe-N/Gra-0.02; (c) Elemental mappings of Fe-N/Gra-0.02; (d) XRD patterns and (e) Raman spectra of Fe-N/Gra catalysts with different Fe loadings after carbonization

Fig. 3 XPS peak-fitting analyses of C, N, and Fe compositions in Fe-N/Gra catalysts (a, b, d) High-resolution XPS spectra of C1s, N1s, and Fe2p for Fe-N/Gra catalysts with different Fe loadings; (c) Comparison of the contents of pyridinic-N, pyrrolic-N, and graphitic-N for Fe-N/Gra catalysts with different Fe loadings. Colorful figures are available on website

Fig. 4 Electrochemical performance characterization of Fe-N/Gra catalysts (0.1 mol·L-1 KOH) (a) LSV curves of Fe-N/Gra catalysts with different Fe loadings in O2-saturated 0.1 mol/L KOH electrolyte at a rotation speed of 1600 r/min; (b) Tafel slopes derived from ORR; (c) LSV curves of Fe-N/Gra-0.02 before and after 3000 cycles; (d) OER curves of Fe-N/Gra catalysts with different Fe loadings; (e) Tafel slopes derived from OER; (f) EIS spectra of Fe-N/Gra catalysts with different Fe loadings; (g) Comparative graph of half-wave potentials for different catalysts and the catalyst in this study[27-35]; (h) Comparison of charge transfer resistance for different catalysts[36-40]. Colorful figures are available on website

Fig. 5 Performance tests of Zn-air battery and schematic illustration of reaction mechanism (a) Schematic diagram of self-assembled Zn-air battery; (b) Polarization curves of the Zn-air battery assembled with Fe-N/Gra-0.02; (c) Discharge performance test of Fe-N/Gra-0.02 at a current density of 10 mA·cm-2; (d) Long-term charge-discharge cycling stability test; (e) Comparative bar chart of apparent current density for different electrocatalysts[27,30 -34,41 -42]; (f) Schematic diagram of valence state changes for Fe2+ and Fe3+ in battery reactions

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