Surface area and thermal stability effect of the MgO supported catalysts for the synthesis of carbon nanotubes

Abstract

Surface area (SA) of the oxide support was found to play a major role on the morphology, quality of the single wall carbon nanotubes (SWNTs) growth. Fe–Co bimetal was supported onto MgO powders with different surface areas, and used for the SWNTs synthesis from the pyrolysis of CH₄ through radio frequency catalytic chemical vapor deposition (RF-CCVD). The high surface area MgO showed specificity towards the growth of SWNTs even at the very high metal loadings of 17.4%. As the MgO surface areas decreased, the agglomeration of the active metal species on the support, nanotubes with wider diameter distributions and more graphitic walls were obtained. This surface area effect suggested that the high surface area networks were responsible for a more effective confinement of the active metal nanoparticles that impeded their migration during the SWNTs thermal growth process. Therefore, by adjusting the surface area or chemical morphology of the catalyst systems, SWNTs with narrower diameter distribution and specific chiralities can be grown.