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 (ΔE) 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.