Cobalt nanoparticles embedded in nitrogen-doped carbon nanotubes for efficient catalysis of oxygen reduction reaction

The oxygen reduction reaction (ORR) is a key process to limit the property of the metal-air batteries. In this paper, cobalt nanoparticles embedded in nitrogen-doped carbon nanotubes (Co-NCNTs) were designed and prepared by pyrolysis of Co-based metal–organic frameworks and cyanoguanidine under an Ar–H₂ atmosphere. The relationship between the morphology and electrocatalytic activity toward ORR was discussed using a variety of physical characterization and electrochemical methods. The obtained Co-NCNT with 3.39 at% nitrogen has a diameter of 30–50 nm. Electrochemical activities of these Co-NCNTs toward ORR in KOH solution were characterized by cyclic voltammetry and rotating disk electrode (RDE) methods. The Co-NCNTs catalysts were also estimated for their stability and methanol-tolerant performance by chronoamperometry in the presence of oxygen. Experimental results display that the onset potential, half-wave potential, Tafel slope and the transferred electron number are 0.95 V (vs. RHE), 0.747 V (vs. RHE), 110.6 mV decade⁻¹ and close to 3, respectively. Moreover, the optimized Co-NCNT has an outstanding durability compared with the commercial Pt/C. This work affords a simple approach for exploring low-cost electrocatalysts with practical performance for metal-air batteries. Graphic abstract:

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