Synthesis of high purity multi-walled carbon nanotubes over Co-Mo/MgO catalyst by the catalytic chemical vapor deposition of methane

Nearly uniform diameter multi-walled carbon nanotubes (MWCNTs) were synthesized over a magnesia supported Co-Mo bimetallic catalyst through the catalytic chemical vapor deposition of methane. The bimetallic catalyst with a composition of Co:Mo:MgO=5:20:75 (mass ratio) was prepared by a sol-gel method. Thermagravimetric analysis shows that MWCNTs were synthesized in high yield. The selectivity of the catalyst for MWCNTs over undesired amorphous carbon was 91.17%. Transmission electron microscopy indicates that the MWCNTs grown on the catalyst have an average diameter of 6.2 ± 0.5 nm (mean ± standard deviation). Through simple purification by mild acid treatment, the catalyst residue for the purified samples was reduced to 0.72%.