Catalytic production of carbon nanotubes by decomposition of CH4 over the pre-reduced catalysts LaNiO3, La4Ni3O10, La3Ni2O7 and La2NiO4

A large amount of more graphitic carbon nanotubes with a narrow size distribution was produced from catalytic decomposition of CH4 over pre-reduced LaNiO3, La(4)Mi(3)O(10), La3Ni2O7 and La2NiO4. The structure and component of fresh and reduced LaNiO3, La4Ni3O10, La3Ni2O7 and La2NiO4 were determined by X-ray diffraction (XRD). The carbon nanotubes obtained were characterized by means of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Thermal oxidation of carbon nanotubes in air was made by thermogravimetric experiments (TG). The results revealed that the value of La/Ni in different catalyst precursors influences the diameter distribution and graphitic degree of carbon nanotubes. Lower La/Ni leads to wider diameter and higher graphitic degree of carbon nanotubes.