Preparation and Oxygen Reduction Reaction Catalytic Performance of Fe, N Co-doped Carbon Nanofibers with Encapsulated Iron Nitride†

doi:10.7503/cjcu20180459

Abstract

Abstract:

Fe, N co-doped porous carbon nanofibers with iron nitride(Fe_xN) nanoparticles encapsulated in Fe, N co-doped carbon shell(Fe_xN@Fe-N-C) were preparated through electrospinning, carbonization and NH₃-etching. The Fe_xN@Fe-N-C catalyst exhibits excellent catalytic activity for oxygen reduction reaction(ORR) in both acid and alkaline media. The half-wave potential(E_1/2) in acidic medium can reach to 0.81 V(vs. RHE), while the E_1/2 in alkaline medium is 0.897 V(vs. RHE), which is even higher than that of commercial Pt/C catalyst. After 10000 cycles of accelerated durability test in acid media, the E_1/2 only decreases by 26 mV, demonstrating the excellent durability of Fe_xN@Fe-N-C. Ion probing and acid-etching experiments indicate that both Fe-N_x sites and Fe_xN nanoparticles contribute to the ORR activity.

Key words: Fe-N-C, Iron nitride, Oxygen reduction reaction(ORR), Carbon nanofibers, NH₃-etching

CLC Number:

O646

TrendMD:

LIU Pei, CHENG Qingqing, CHEN Chi, ZOU Liangliang, ZOU Zhiqing, YANG Hui. Preparation and Oxygen Reduction Reaction Catalytic Performance of Fe, N Co-doped Carbon Nanofibers with Encapsulated Iron Nitride^†[J]. Chem. J. Chinese Universities, 2018, 39(11): 2492.

Figures/Tables 12

Scheme 1 Schematic illustration of the synthesis of FexN@Fe-N-C catalysts

Fig.1 TEM images of the Fe-N-CNF after carbonization and acid-leaching(A) and FexN@Fe-N-C-20 after NH3-treatment for 20 min(B) and high-resolution TEM image of FexN nanoparticle(C)

Fig.2 TEM images(A, A') and the elemental EDS-mapping analysis(B—D, B'—D') of C, N and Fe in the regions of FexN nanoparticle(A—D) and carbon nanofiber(A'—D') in FexN@Fe-N-C-20

Fig.3 XRD patterns of Fe-N-CNF(a) and FexN@Fe-N-C-20(b)

Fig.4 N2 adsorption/desorption isotherms(A) and pore size distributions(B) of Fe-N-CNF(a) and FexN@Fe-N-C-20(b)

Fig.5 XPS survey spectrum of FexN@Fe-N-C-20(A) and Raman spectra of Fe-N-CNF(a) and FexN@Fe-N-C-20(b)(B)Inset shows the deconvoluted high-resolution N1s XPS spectrum.

Table 1 Atomic fractions(%) of Fe-N-CNF and FexN@Fe-N-C-t(t=10, 20, 40) measured by XPS

Sample	C	N	O	Fe
Fe-N-CNF	85.63	3.38	10.40	0.59
Fe_xN@Fe-N-C-10	92.61	3.30	4.28	0.36
Fe_xN@Fe-N-C-20	93.09	3.25	3.32	0.34
Fe_xN@Fe-N-C-40	95.30	2.01	2.36	0.32

Fig.6 ORR polarization curves of Fe-N-CNF, FexN@Fe-N-C-t(t=10, 20, 40) and Pt/C in O2-saturated 0.1 mol/L HClO4(A), ORR polarization curves of FexN@Fe-N-C-20 at various rotation rates in 0.1 mol/L HClO4(B) and the corresponding K-L plots at various potentials(C)

Fig.7 ORR polarization curves of FexN@Fe-N-C-20 and Pt/C in O2-saturated 0.1 mol/L KOH(A), ORR polarization curves of FexN@Fe-N-C-20 at various rotation rates in 0.1 mol/L KOH(B) and the corresponding K-L plots at various potentials(C)

Fig.8 ORR polarization curves of FexN@Fe-N-C-20(A) and Pt/C(B) before and after 10000 cycles of accelerated durability test in O2-saturated 0.1 mol/L HClO4Potential range: 0.6—1.0 V; scan rate: 50 mV/s.

Fig.9 ORR polarization curves of N/CNF and FexN@Fe-N-C-20 with various amount of SCN- in 0.1 mol/L HClO4(A) and the comparison of the corresponding half-wave potentials(B)a. Initial; b. 5 mL SCN-; c. 25 mL SCN-; d. 40 mL SCN-; e. N/CNF.

Fig.10 ORR polarization curves of FexN@Fe-N-C-20 before and after second acid-leaching in 0.1 mol/L HClO4(A) and ORR polarization curves of Fe-N/CNF-H2, Fe-N/CNF-N2 and FexN@Fe-N-C-20(B)

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