Effect of Manganese Addition to the Co-MCM-41 Catalyst in the Selective Synthesis of Single Wall Carbon Nanotubes

The effect of manganese addition to the Co-MCM-41 catalyst on the synthesis of single wall carbon nanotubes (SWNT) by CO disproportionation was characterized. The ratio between the two metals in the MCM-41 framework was varied, and its effect on the resultant SWNT distribution was studied and compared with the results obtained for the monometallic Co-MCM-41 catalyst. Methods including temperature-programmed reduction, X-ray absorption fine structure, thermogravimetric analysis, TEM imaging, and Raman and fluorescence spectroscopy were employed to characterize the behavior of the catalysts under the SWNT synthesis conditions and the diameter and Structure distribution of the resultant nanotubes. We found that addition of Mn to the Co-MCM-41 catalyst promotes the growth of SWNT, leading to synthesis of high yield, small diameter SWNT. Manganese does not act in the nucleation of SWNT but acts as an anchoring site for cobalt particles formed during the synthesis process as shown by X-ray absorption.