Role of surface cobalt silicate in single-walled carbon nanotube synthesis from silica-supported cobalt catalysts.

A silica-supported cobalt catalyst has been developed via incipient wetness impregnation for high-yield synthesis of single-walled carbon nanotubes (SWNTs). Co/SiO2-impregnated catalysts have not been observed to be efficient for SWNT synthesis. Using an appropriately chosen precursor, we show that effective catalysts can be obtained for SWNT synthesis with yields up to 75 wt %. Detailed characterization indicates that the active sites for SWNT synthesis are small cobalt particles resulting from the reduction of a highly dispersed surface cobalt silicate species. The SWNTs produced by this catalyst are of high quality and easy to purify, and the process is simple and scalable.