Sp² C‐Dominant N‐Doped Carbon Sub‐micrometer Spheres with a Tunable Size: A Versatile Platform for Highly Efficient Oxygen‐Reduction Catalysts

Abstract

A simple, yet versatile strategy to prepare size-controlled and monodisperse carbon sub-micrometer spheres is developed based on the biomolecule dopamine. Unlike traditional carbon materials, the resulting carbon sub-micrometer spheres contain much less sp(3) carbon with high-level electroactive nitrogen. Moreover, metal-carbon hybrid sub-micrometer spheres can be easily obtained, and show highly promising catalytic properties in the oxygen-reduction reaction.

Cobalt Oxide and Cobalt‐Graphitic Carbon Core–Shell Based Catalysts with Remarkably High Oxygen Reduction Reaction Activity

“…We attribute this to the chelation of Co (III) by EDTA in aqueous solution forming essentially six‐coordination complexes of Co center with two nitrogens and four oxygens from EDTA which have unpaired electrons 19. N 1s XPS spectra provide an additional hint into the possibility of ORR activity contribution from nitrogen‐doped carbon as reported in several works 5, 6, 7. Comparison between the spectra of CoO x /Co@GC‐NC and CoO x /Co@GC‐NC‐0 (Figure 2c; Figure S7c, Supporting Information; the results of which are summarized in Table S2, Supporting Information) establishes the dominant presence of pyridinic nitrogen in the most active catalyst.…”

“…Nitrogen‐doped carbon also favors enhanced ORR activity which was attributed to the activity of the pyridinic nitrogen sites by most studies 5, 6. Distinct N active sites were reported to have distinct role where typically pyridinic N contributes to improved onset potential whereas graphitic N facilitates enhanced current density 7. Other N sites, such as pyrrolic N and oxidized N, may also exist, but they are not reported to be catalytically active.…”

Metal–Organic‐Framework‐Derived Dual Metal‐ and Nitrogen‐Doped Carbon as Efficient and Robust Oxygen Reduction Reaction Catalysts for Microbial Fuel Cells

“…Thus, replacing the noble metal based cathode catalyst with the low‐cost catalyst is a favorable approach to reduce the cost of MFCs. Up to now, significant research efforts have been devoted to the exploration of alternative ORR catalysts, and some inexpensive ORR catalysts, such as metal oxide5, 6, 7, 8 and nonmetal heteroatom doped carbon,9, 10, 11, 12, 13, 14, 15, 16 have been developed for the replacing of Pt‐based catalysts. However, it is still challenging to achieve satisfying ORR performance with these inexpensive catalysts due to the sluggish kinetics of ORR.…”

Sub‐50 nm Iron–Nitrogen‐Doped Hollow Carbon Sphere‐Encapsulated Iron Carbide Nanoparticles as Efficient Oxygen Reduction Catalysts

“…Fe 3 C‐Fe,N/C‐900 exhibited a high half‐wave potential of ≈0.881 V, which is comparable to that of commercially available Pt/C ( E 1/2 = 0.878 V). Poor ORR performance was observed on N/C‐900 with a negative shift in the half‐wave potential to ≈0.719 V. Compared to previously reported remarkable nitrogen‐doped carbon‐encapsulated Fe 3 C catalysts (Table S2, Supporting Information), Fe 3 C‐Fe,N/C‐900 still exhibited noticeable ORR electrocatalytic activity in alkaline media 28, 29, 32, 58. However, in 0.1 m HClO 4 , Fe 3 C‐Fe,N/C‐900 exhibited a slightly negative shift in the LSV curve.…”