Design of new catalyst precursors for synthesis of carbon nanotubes with high purity and aspect ratio using deep-injection floating-catalyst chemical vapor deposition

The continuous production of carbon nanotubes (CNTs) with high crystallinity, high purity, and especially high aspect ratio significantly increases the possibility for widespread usage of CNTs in various industrial applications. In this work, new types of catalyst precursors are designed for the formation of small and uniform catalyst particles and thus synthesis of CNTs with high aspect ratio using deep-injection floating catalyst chemical vapor deposition method. Ferrocene derivatives containing functional groups with electron-withdrawing properties are observed to possess higher decomposition temperatures than ferrocene by in situ TEM analysis. As a new catalyst precursor, an acetyl-ferrocene, a ferrocene derivative with higher decomposition temperature than ferrocene contributes to synthesize CNTs with higher purity and aspect ratio due to the formation of smaller and more uniform catalyst particles. The use of a new type of catalyst precursor and optimization of sulfur injection amount allow to synthesize CNTs with an ultra-high aspect ratio of ~24,000, less necessity for additional purification process (<4% of residual contents) for their applications. • In-situ TEM observation for thermal decomposition behavior of various ferrocene derivatives. • DFT simulation for predicting the dissociation mechanisms of ferrocene derivatives. • The use of different catalyst precursors leads to variations in the synthesis results and optimal sulfur concentration. • CNTs with high crystallinity ( I G / I D ~ 54.9), high purity (~97%) and high aspect ratio (~24,000) were synthesize.