Iron–Nitrogen‐Doped Vertically Aligned Carbon Nanotube Electrocatalyst for the Oxygen Reduction Reaction

Abstract

A highly active iron-nitrogen-doped carbon nanotube catalyst for the oxygen reduction reaction (ORR) is produced by employing vertically aligned carbon nanotubes (VA-CNT) with a high specifi c surface area and iron(II) phthalocyanine (FePc) molecules. Pyrolyzing the composite easily transforms the adsorbed FePc molecules into a large number of iron coordinated nitrogen functionalized nanographene (Fe-N-C) structures, which serve as ORR active sites on the individual VA-CNT surfaces. The catalyst exhibits a high ORR activity, with onset and halfwave potentials of 0.97 and 0.79 V, respectively, versus reversible hydrogen electrode, a high selectivity of above 3.92 electron transfer number, and a high electrochemical durability, with a 17 mV negative shift of E 1/2 after 10 000 cycles in an oxygen-saturated 0.5 M H 2 SO 4 solution. The catalyst demonstrates one of the highest ORR performances in previously reported any-nanotube-based catalysts in acid media. The excellent ORR performance can be attributed to the formation of a greater number of catalytically active Fe-N-C centers and their dense immobilization on individual tubes, in addition to more effi cient mass transport due to the mesoporous nature of the VA-CNTs.

N-doped carbon nanotubes containing a high concentration of single iron atoms for efficient oxygen reduction

“…To the best of our knowledge, our CNT@Fe-N-PC catalyst showed the best ORR performance in an acidic medium compared with all previously reported Fe-N-C and other non-noble-metal catalysts (Supplementary Table 2). 11,12,13,20,22,27,28,31,[37][38][39][40] In addition to the high activity, we further studied the durability of the CNT@Fe-N-PC catalyst. Figure 3c shows that the current density decay is 12% after 40 000 s of testing, much smaller than that (57%) of commercial Pt/C.…”

“…Notable progress has been made in recent years in the development of low-cost noble-metal-free catalysts, including heteroatom-doped carbon materials, 4-6 Fe 3 C-based materials [7][8][9] and transition-metalcoordinated nitrogen-doped carbon catalysts (Me-N-C, Me: Fe and/ or Co). [10][11][12] Although these materials demonstrate desirable ORR catalytic activity comparable to that of Pt/C in an alkaline medium, only Me-N-C catalysts, particularly Fe-N-C, show relatively good catalytic activity and durability in acidic conditions, [13][14][15] which makes them attractive for use in proton exchange membrane fuel cells. Fe-N-C catalysts are generally synthesized by pyrolyzing precursors containing carbon, nitrogen, and iron at temperatures above 700°C, to achieve high activity and a robust structure.…”

Binary Nitrogen Precursor-Derived Porous Fe-N-S/C Catalyst for Efficient Oxygen Reduction Reaction in a Zn-Air Battery

“…Figure 2b-d display the high resolution N 1s spectra of the three Fe-NS/PC catalysts. All the spectra can be deconvoluted into four peaks corresponding to pyridinic N (N1, 398.1-398.7 eV), pyrrolic N (N2, 399.78-400.7 eV), graphitic N (N3, 400.99-401.3 eV), and oxidized N (N4, 402-404.27 eV) [25,26], respectively. Previous reports have demonstrated that both pyridinic N and graphitic N may participate the oxygen reduction reaction [27][28][29].…”

Biomass Derived N-Doped Porous Carbon Supported Single Fe Atoms as Superior Electrocatalysts for Oxygen Reduction

“…[28][29][30] Moreover, for tuning the coordination of Fe atoms, the traditional methods mainly focus on introducing the reacting gas atmosphere (e.g., NH 3 ) during the pyrolysis treatment, or adding extra ligand species (e.g., pyridine and imidazole) for Fe atoms. [21,24,31] Nevertheless, it still remains a large challenge to prepare single-atomic Fe catalysts by a facial and effective method for their commercial and technological feasibility.…”

“…[15,[21][22][23] Although the original Fe-N 4 moieties (e.g., the central part of iron phthalocyanine) have been proven to be the highly active sites for ORR, the coordination environment of Fe still needs to be optimized. [24,25] Considering that the high-temperature heat-treatment may make the Fe atoms aggregate and break the N-contained functional groups, [26] choosing an appropriate support material or tuning the coordination environment for Fe may be the important step to prepare high-performance SACs of Fe.…”