A study on carbon nanotubes prepared from catalytic decomposition of C2H2 or CH4 over the pre-reduced LaCoO3 perovskite precursor

A large amount of carbon nanotubes with uniform diameter were produced from catalytic decomposition of C2H2 or CH4 over perovskite oxide LaCoO3 cataly st precersor. The result of XRD measurement indicated that after reduction of LaCoO3 at 700 degreesC cobalt existed chiefly as Co-0 particles supporte d and separated by La2O3. La2O3 can prevent Co-0 from agglomeration. The si ze of Co-0 nanoparticles determined the diameter of carbon nanotubes. The m orphologies and microscopic structure of carbon nanotubes were examined by means of scanning electron microscopy (SEM), transmission electron microsco py (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) a nd Raman. Reduction of LaCoO3 in H-2 and thermal oxidation of carbon nanotu bes in air were made by thermogravimetric experiments (TG). XPS and Raman r esults revealed that the carbon nanotubes made from CH4 are probably more g raphitized than those made from C2H2.