Growth of single and double walled carbon nanotubes over Co/V/MgO catalysts

[Display omitted] ► Co/V/MgO has remarkable catalytic activity on the growth of SWCNTs and DWCNTs. ► The diameter of CNTs can be controlled by adjusting molar ratio of Co–V to MgO. ► The formation of C 7V 8 is critical to the synthesis of thin CNTs. High quality single walled carbon nanotubes (SWCNTs) and double walled carbon nanotubes (DWCNTs) were synthesized on Co/V/MgO catalysts by catalytic decomposition of CH 4 in H 2. Raman spectroscopy data revealed that the diameters of as-prepared SWCNTs are 1.28 and 0.73 nm. The diameter value of DWCNTs from Raman analysis also showed a narrow diameter distribution. Using field emission transmission electron microscopy (TEM), it was found that the diameter of carbon nanotubes can be controlled mainly by adjusting the molar ratio of Co–V versus the MgO support. The structure properties of catalysts were examined by X-ray diffraction (XRD). The formation of C 7V 8 may play an important role in preserving carbon in the catalyst particle and favoring the dissociation balance of CH 4.