Co3O4/Co nanoparticles coated with nitrogen-doped graphitized porous carbon frameworks(Co3O4/Co-NC)were synthesized via annealing Co-based metal-organic-frameworks(ZIF-67)using cobalt nitrate hexahydrate and 2-methylimidazole as raw materials.The bifunctional electrocatalyst consisting of Co3O4/Co-NC with three-dimensional porous structure was investigated for Zn-air batter-ies.It was found that this unique structure offered an efficient charge transport environment.In addi-tion,the strong binding forces between nanoparticles and carbon frameworks through Co-N covalent bonds prevented the loss of nanoparticles from the electrocatalysts,thus demonstrating good bifunc-tional electrocatalytic activity.Co3O4/Co-NC exhibited good oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)performances with a half-wave potential of 0.844 V and the low overpotential of 424 mV at 10 mA/cm2 in 0.1 mol/L KOH solution.A Zn-air battery driven by the Co3O4/Co-NC catalyst exhibited good charge/discharge performance,with a power density of 116.69 mW/cm2,and long-term cycling stability for 51 h,possessing good potential for practical ap-plication in next-generation rechargeable batteries.
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