N,O-codoped carbon spheres with uniform mesoporous entangled Co 3 O 4 nanoparticles as a highly efficient electrocatalyst for oxygen reduction in a Zn-air battery.

Highly efficient electrochemical catalysts for oxygen reduction reactions (ORRs) are urgently needed for various energy conversion and storage devices to overcome sluggish ORR kinetics. Here, N,O-codoped carbon spheres with uniform mesopores and a high specific surface area were used as supports for decorating Co ₃ O ₄ nanoparticles via a facile immersion route. In addition to the benefit of ions and gas mass transfer, the abundant mesopores present in the three-dimensional (3D) carbon spheres also confine and isolate the Co ₃ O ₄ nanoparticles growing in it, which help to provide rich Co ₃ O ₄ active sites. The resulting hybrid material exhibits superior ORR activity in terms of even-better half-wave potential and stability than that of commercial Pt/C (40 wt%) in 0.1 M KOH electrolyte. To verify its catalytic activity, the hybrid material was employed as the cathode catalyst in a flexible solid-state zinc-air battery, which achieves a high power density of 227 mW cm ^-2 ; this power density is much higher than that of a Pt/C catalytic zinc-air battery (133 mW cm ^-2 ) under identical conditions. The improvement in catalytic activity in both aqueous and nonaqueous electrolytes can be attributed to the abundant active sites of the entangled Co ₃ O ₄ nanoparticles, as well as the novel N,O-codoped carbon structure.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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