Honeycomb-like Carbon-supported Fe Single Atom Catalyst: Preparation and Electrocatalytic Performance in Oxygen Reduction Reaction

doi:10.15541/jim20200624

Abstract

Abstract:

Single atom catalysts (SACs) have emerged as an attractive concept for promoting heterogeneous reactions due to the unique properties, such as high activity and nearly 100% atom utilization. However, the synthesis of SACs remains a challenge due to the sintering of metal atoms at high temperature. In this study, Fe single atom on N doped porous carbon (Fe SA-NC) catalyst was obtained by ultrastrong polarity of molten salt (MS). Fe SA-NC shows honeycomb-like porous morphology and possesses a high specific surface area of 2072 m²·g^-1. The content of Fe element in Fe SA-NC is 0.57wt%. The isolated Fe atoms are observed by AC HAADF-STEM, and the X-ray absorption fine structure (XAFS) analysis confirms that Fe atoms disperse in the form of Fe-N₄ on the carbon substrate. Fe SA-NC shows 0.85 V half-wave potential and 5.79 mA·cm^-2maximum current density for ORR in 0.1 mol/L KOH solution. Fe SA-NC displays high selectivity for ORR four electron pathway (H₂O₂ yield<2%, electron transfer number is 3.9), outstanding stability, and good methanol tolerance.

Key words: single atom catalyst, porous, nitrogen-doped carbons, oxygen reduction reaction

CLC Number:

O646

LIU Ziruo, LIU Wei, HAO Ce, HU Jinwen, SHI Yantao. Honeycomb-like Carbon-supported Fe Single Atom Catalyst: Preparation and Electrocatalytic Performance in Oxygen Reduction Reaction[J]. Journal of Inorganic Materials, 2021, 36(9): 943-949.

Figures/Tables 8

Fig. 1 SEM images of (a) Fe-NC and (b)Fe SA-NC, (c)nitrogen adsorption/desorption plots of Fe SA-NC at 77 K, and (d) pore size distribution of Fe SA-NC

Fig. 2 (a) TGA curves of hypoxanthine and hypoxanthine with molten salt; (b) Raman spectra and (c) XRD patterns of Fe SA-NC and Fe-NC

Fig. 3 (a, b) AC HAADF-STEM images, high-resolution X-ray photoelectron spectra (XPS) of (c) N1s and (c) Fe2p of the Fe SA-NC catalyst

Table 1 XPS results of element composition in Fe SA-NC catalyst

Element	C	N	O	Fe
Atomatic percent/%	74.54	14.18	10.15	0.60

Fig. 4 Fe K-edge (a) XANES spectra (b) k2-weighted FT spectra for the Fe SA-NC, FePc, FeO and Fe2O3 and (c) EXAFS fitting curves in R space for Fe SA-NC Insets in (c): EXAFS fitting curves in k space (up) and schematic models of Fe SA-NC (down); C (gray), N (blue), Fe (orange), O (red)

Table 2 EXAFS fitting parameters of Fe SA-NC sample

Sample	Path	N	R/nm	σ²/(×10^-5, nm²)	ΔE₀/eV	R factor
Fe SA-NC	Fe-N	3.9	0.209	5.7	4.7	0.093
Fe SA-NC	Fe-O	1.0	0.190	5.7	4.7	0.093

Fig. 5 (a) CV curves of the Fe SA-NC in a N2-saturated and O2-saturated 0.1 mol/L KOH solution, respectively; (b) LSV curves of Fe SA-NC, NC and Pt/C in O2-saturated 0.1 mol/L KOH solution (1600 r/min, 10 mV·s-1); (c) ORR polarization curves of Fe SA-NC recorded at different rotating speeds; (d) K-L plots derived from Fig. (c); (e) ORR electron transfer number and H2O2 yield of Fe SA-NC; (f) Tafel slopes of Fe SA-NC, NC and Pt/C in O2-saturated 0.1 mol/L KOH solution

Fig. 6 (a) Durability test and (b) methanol resistance test for Fe SA-NC in O2-saturated 0.1 mol/L KOH solution (1600 r/min)

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