Correlating the fluctuated growth of carbon nanotubes with catalyst evolution by atmospheric-pressure environmental transmission electron microscopy

Rate-controlled growth of carbon nanotubes (CNTs) and catalyst design are considered efficient ways for the preparation of CNTs with specific structures and properties. However, due to the difficulties in capturing the growth process of the CNTs with tiny size under a complex growth environment, the growth kinetics of CNTs and their correlation with the catalyst seed have been seldom revealed. Here, we investigated the growth process of CNTs from Ni nanoparticles (NPs) in real-time under atmospheric pressure using transmission electron microscopy equipped with a closed gas cell. It was found that the growth rates of CNTs fluctuated, and a phase transition from Ni₃C to Ni, and a reshaping of the catalyst NPs occurred during the growth process. We demonstrated that CNTs dynamically interacted with the connected catalyst NPs and the fluctuated growth rates of CNTs were correlated with the structure change of catalyst NPs. The origin of the growth rate fluctuation is attributed to the change of carbon concentration gradient in catalyst NPs.