Synergism of Co and Mo in the catalytic production of single- wall carbon nanotubes by decomposition of CO

The catalyst composition and operating conditions for the synthesis of single-wall carbon nanotubes (SWNT) from CO decomposition have been systematically varied in order to maximize the selectivity towards SWNT. A simple quantification method based on the standard Temperature Programmed Oxidation (TPO) technique has allowed us to determine the distribution of the different forms of carbonaceous deposits present on the catalysts after the CO decomposition reaction. A synergistic effect between Co and Mo has been observed. When both metals are simultaneously present, particularly when Mo is in excess, the catalyst is very effective. However, when they are separated they are either inactive (Mo alone) or unselective (Co alone). To understand this synergistic effect, X-ray absorption spectroscopy (EXAFS and XANES) has been used to characterize the state of Co and Mo on the catalysts before and after the production of SWNT. © 2001 Published by Elsevier Science Ltd.