Synthesis of NbC@C(Nx) nanoparticles using DC arc discharge plasma for highly efficient oxygen reduction reaction.

Development of the low-cost, high-efficiency, and durable non-precious metal electrocatalysts for cathodic oxygen reduction reaction (ORR) is of vital importance for fuel cells and metal-air batteries. Herein, the carbon-coated NbC nanoparticles (NbC@C NPs) were prepared using DC arc discharge plasma under a methane atmosphere. Then, the nitrogen-doping was conducted by heat treatment, resulting in nitrogen-doped carbon-coated NbC nanoparticles (NbC@C(N x) NPs). Benefiting from the merit of unique core-shell structure and best synergy between the nitrogen-doped carbon shell and the NbC core, the obtained highest nitrogen-doped NbC@C(N 1.36) NPs showed an onset potential (E onset) of 0.89 V (vs. RHE) and a half-wave potential (E 1/2) of 0.79 V, which are comparable to those of commercial Pt/C (20 wt%) (E onset = 0.90 V, E 1/2 = 0.80 V), and its diffusion-limited current density (J L) of 5.99 mA·cm−2 is even higher than that of commercial Pt/C (5.43 mA·cm−2). Moreover, it exhibited a remarkable long-term durability and impressive methanol resistance than Pt/C catalyst. In addition, the real-time optical emission spectrum (OES) analysis of arc plasma shows that the electron temperature (T e) is 7562.9 K in local thermal equilibrium (LTE) plasma. Therefore, the use of the DC arc discharge plasma method opens a fast and simple way to develop cost-effective and highly efficient non-precious metal catalysts for ORR. [Display omitted] • Prepared NbC NPs using a DC arc discharge plasma method show a core-shell structure. • N-doping induces surface electronic structure modification of the graphitic shell, creating the ORR additional active sites. • The electron transfer number of NbC@C(N x) NPs indicates that the reaction path is close to a 4-electron process. • The energy state of the working arc plasma is diagnosed by means of real-time optical emission spectroscopy. [ABSTRACT FROM AUTHOR]