Co single atoms and nanoparticles dispersed on N-doped carbon nanotube as high-performance catalysts for Zn-air batteries

Diminishing the size of active sites in catalysts is promising to improve the kinetics of oxygen reduction reaction (ORR) and reduce the cost of metal–air batteries. However, the facile preparation of high-performance catalysts with nanoscale active sites still suffers from great challenge. Herein, we report a facile template-free strategy to fabricate Co single atoms and nanoparticles dispersed on porous N-doped carbon nanotube (Co-NCNT) by the pyrolysis of the composites of metal–organic complexes and porous carbon nanotube. Different from the conventional strategy, the precursor metal–organic complexes in this work were prepared under mild conditions and used without complex purification procedures. Compared with the pristine carbon nanotube, N-doped carbon nanotube with abundant mesopores contribute to the formation of nanoscale Co sites. This resultant electrocatalyst Co-NCNT shows an impressive ORR half-wave potential of 0.87 V in alkaline solution, outperforming that of commercial Pt/C (20 wt%). The catalyst Co-NCNT displays high tolerance to strong alkali solution, endowing the aqueous Zn-air batteries with high discharge voltages and power density. In addition, the specific capacity achieves 803 mAh·g_Zn⁻¹ under a current density of 10 mA·cm⁻¹. This research provides a new solution for the simple synthesis of carbon-based electrocatalysts for metal–air batteries.