Abstract
Sub‐50 nm iron–nitrogen‐doped hollow carbon sphere‐encapsulated iron carbide nanoparticles (Fe3C‐Fe,N/C) are synthesized by using a triblock copolymer of poly(styrene‐b‐2‐vinylpyridine‐b‐ethylene oxide) as a soft template. Their typical features, including a large surface area (879.5 m2 g−1), small hollow size (≈16 nm), and nitrogen‐doped mesoporous carbon shell, and encapsulated Fe3C nanoparticles generate a highly active oxygen reduction reaction (ORR) performance. Fe3C‐Fe,N/C hollow spheres exhibit an ORR performance comparable to that of commercially available 20 wt% Pt/C in alkaline electrolyte, with a similar half‐wave potential, an electron transfer number close to 4, and lower H2O2 yield of less than 5%. It also shows noticeable ORR catalytic activity under acidic conditions, with a high half‐wave potential of 0.714 V, which is only 59 mV lower than that of 20 wt% Pt/C. Moreover, Fe3C‐Fe,N/C has remarkable long‐term durability and tolerance to methanol poisoning, exceeding Pt/C regardless of the electrolyte.
Highlights
In addition to the chemical composition, the ORR performance is closely correlated to the morphology of the Fe–nitrogen-doped carbon (N/C)The oxygen reduction reaction (ORR) on the cathode is a major catalysts
Fe3C-Fe,N/C hollow spheres exhibit an ORR performance comparable to that of commercially available 20 wt% Pt/C in alkaline electrolyte, with a similar half-wave potential, an electron transfer number close to 4, and lower H2O2 yield of less than 5%
Our sub-50 nm hollow Fe3C-Fe,N/C-900 spheres show comparable ORR performance to that of commercially available 20 wt% Pt/C (Pt/C) in both alkaline and acidic media, which is mainly due to the following synergetic contribution of the compositions and morphologies: (i) well-distributed Fe3C nanoparticles encapsulated in hollow carbon spheres; (ii) high content of pyridinic N and graphitic N that can form active sites; (iii) large surface area and porous shells that allow the exposure of active sites and rapid mass-transfer kinetics; and (iv) small hollow size (
Summary
In addition to the chemical composition, the ORR performance is closely correlated to the morphology of the Fe–N/C. Fe–N/C catalysts show excellent ORR performance in alkaline electrolytes, few groups have reported electrocatalytic activities comparable to those of commercially available catalysts in acidic electrolytes.[26,29,41] our sub-50 nm hollow Fe3C-Fe,N/C-900 spheres show comparable ORR performance to that of commercially available 20 wt% Pt/C (Pt/C) in both alkaline and acidic media, which is mainly due to the following synergetic contribution of the compositions and morphologies: (i) well-distributed Fe3C nanoparticles encapsulated in hollow carbon spheres; (ii) high content of pyridinic N and graphitic N that can form active sites; (iii) large surface area and porous shells that allow the exposure of active sites and rapid mass-transfer kinetics; and (iv) small hollow size (
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