A scalable CVD synthesis of high-purity single-walled carbon nanotubes with porous MgO as support material

Abstract

The choice of support and catalyst materials has been proved to be critical to scalable chemical vapor deposition (CVD) synthesis of carbon nanotubes. In our study, we found that porous MgO prepared by thermal decomposition of its salts was an eminent support material for CVD growth of single-walled carbon nanotubes (SWNTs). Compared with other kinds of supports such as SiO2, ZrO2, Al2O3 and CaO etc., the quality of as-grown SWNTs on MgO supports was stable; the effects of reaction conditions such as furnace temperature, flow rate of the gas and the types of catalysts and supports on the properties of as-prepared SWNT products were thoroughly investigated and characterized by micro-Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetry (TG) techniques. The results indicated that the yields of SWNTs on MgO supports could be up to about 120% with the addition of a small amount of assistant catalyst Mo salt. The obtained purity of the as-grown products was higher than 90% after treatment with 4 M HCl. The obvious advantages of using MgO supports include efficient and stable growth of SWNTs, scalable synthesis of SWNTs at low cost, and easy removal of the support in mild acid, causing little harm to the products.