Unique bubble-chain carbon nanotubes catalyzed by CoZn nanoparticles

Abstract

Carbon nanomaterials with combined structures are highly desirable in both fundamental research and industrial applications. Herein, we report a unique carbon bubble-chain N-doped carbon nanotubes (CNTs) with features of both nanospheres and nanotubes prepared by a facile pyrolysis method. The in situ formed CoZn alloy which acts as a novel catalyst for the bubble-chain CNTs is found to be an intermetallic compound with a face-centered cubic structure. Compared with typical Fe, Co, and Ni catalysts, CoZn has larger unit cell parameters with larger tetrahedral and octahedral interstices, resulting in the fast C/N diffusion across the catalyst. In addition, CoZn catalyst is partially melted at the CNTs growth temperature. We demonstrate that the high N content, the fast C/N diffusion and the partially molten CoZn catalyst contribute to the growth of bubble-chain CNTs at moderate temperature. Bubble-chain nanotubes can be described as a unique carbon structure between carbon hollow nanospheres and nanotubes, which may have the advantages of both nanospheres and nanotubes. The formation mechanism of bubble-chain N-doped CNTs and the electrocatalytic properties towards oxygen reduction reaction were presented in this work.