Here, we successfully synthesized N-doped carbon nanotubes embedded with nickel-based nanoparticles on the top (N-CNTs/ E-NNPs) by directly procedural calcination of melamine and nickel foam at 520°C, 540°C and 700°C in Ar. When applied for oxygen reduction reaction (ORR), the onset potential and halfwave potential are 0.96 V and 0.86 V in 0.1 M KOH, comparable to that of the commercial 10 wt% Pt/C. Moreover, the hybrids possess higher stability and better methanol tolerance. Additionally, the Tafel slope of N-CNTs/E-NNPs is 76 mV dec À 1 in 0.1 M KOH, lower than 83 mV dec À 1 of the commercial 10 wt% Pt/C, demonstrating a good kinetic process. The remarkable features are mainly ascribed to synergistic enhancement effect from N-rich doped carbon nanotubes (N-CNTs) and embedded Ni-based nanoparticles on the top, promoting mass and electrons transport, enhancing the activity of active sites and making it a promising highly efficient non-precious metal ORR catalyst.

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Here, we report nano-mediated Cu–Co–Ni-based nitrogen-doped carbon nanotubes (N-CNTs/T-CCN) by hydrothermal and procedural calcination strategy. The nitrogen-doped carbon nanotubes (N-CNTs) show more average diameter and the N-CNTs are uniformly modified with ternary Cu–Co–Ni-based nanoparticles (T-CCN). The hybrid exhibits excellent ORR catalytic activity. The onset potential (Eonset) and half-wave potential (E1/2) are 0.96 V and 0.87 V (versus reversible hydrogen electrode, RHE) in 0.1 M KOH. Most importantly, compared to 20% Pt/C, N-CNTs/T-CCN catalyst displays better methanol tolerance and higher stability. The H2O2 yield of the N-CNTs/T-CCN is less than 7.5% and the electron-transfer number (n) is about 3.9. High ORR performance may be related to the synergistic enhancement effect. The N-CNTs supply good electrical conductivity and allow large numbers of active sites to efficiently participate; the T-CCN can improve the local work function of the N-CNTs by synergistic electronic interaction and promote O2 adsorption; the stability of embedded T-CCN can be greatly improved, mainly due to the weakness of Ostwald effect. All these advantages make the hybrid a promising ORR catalyst.