Facile synthesis of cobalt nanoparticles encapsulated in nitrogen-doped carbon nanotubes for use as a highly efficient bifunctional catalyst in rechargeable Zn-Air batteries

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have a critical function as the cathode reactions in rechargeable Zn-air batteries. In this work, a facile strategy for the scalable fabrication of cobalt nanoparticles encapsulated in nitrogen-doped carbon nanotubes (Co@NC) was used. The experimental results and density functional theory calculations demonstrated that carbon nanotubes with a good graphitization degree were obtained by introducing a certain amount of cobalt species. The Co@NC-3 catalyst exhibited good catalytic performance, with a potential gap (DE) between the E-j=10 value of the OER and ORR half-wave potential (E-1/2) of only 0.816 V, which is lower than that of many highly efficient bifunctional catalysts reported in the literature. Moreover, rechargeable Zn-air batteries based on the Co@NC-3 catalyst generated a high power density (163.4 mW.cm(-2)) and specific capacity (795.5 mA h.g(-1) at 10 mA.cm(-2)). The results confirm that Co@NC-3 could be used as a highly efficient bifunctional catalyst for renewable energy conversion devices. (C) 2020 Elsevier B.V. All rights reserved.