Purity-controllable growth of bamboo-like multi-walled carbon nanotubes over copper-based catalysts

The growth of bamboo-like multi-walled carbon nanotubes (CNTs) without the formation of amorphous carbons was performed using copper-based catalysts by catalytic chemical vapour deposition (CVD) with diluted ethylene at 700–900 °C. The as-grown CNT soot was characterised by transmission electron microscopy, thermogravimetric analysis and Raman spectroscopy. The weak metal–support interaction of a sulphate-assisted copper catalyst (CuSO4/SiO2) can provide high-purity growth with remarkable yields of CNTs (2.24–6.10 CNT/g Cu·h) at 850–900 °C. Additionally, hydrogen-assisted CVD can activate inert copper catalysts, e.g., Cu(NO3)2/SiO2 or Cu(CH3COO)2/SiO2, for the growth of CNTs.

► We report a method to grow carbon nanotubes without the formation of amorphous carbons.
► Weak metal–support interaction of sulphate-assisted copper catalysts can improve the growth quality of CNTs.
► The CNT growth yields will significantly increase at 800–900 °C.
► Hydrogen-assisted CVD can activate inner copper catalysts for the CNT growth.