Effect of process conditions on the synthesis of carbon nanotubes by catalytic decomposition of methane

A new dual-composition catalyst based on Ni–Mo/MgO with high efficiency of producing carbon nanotubes (CNTs) from methane was reported recently. In the present article, with this type of catalyst, the impact of such experimental parameters as reaction temperature, reaction time, concentration of H₂, flow rate ratio of CH₄ to H₂ on yield and graphitization were investigated, leading to the following optimal growth conditions: reaction time 60 min, reaction temperature 900 °C, CH₄:H₂ about 100:20 mL/min, under which high-yield multi-walled CNTs bundles were synthesized. Raman measurement indicated that the as-synthesized product was well-graphitized, and the purity was estimated over 95% by TG–DSC analysis. In terms of the above results, an explanation of high-efficiency formation of CNTs bundles and the co-catalysis mechanism of Ni–Mo/MgO were suggested.