(706f) Sulfur Doped Co/SiO2 Catalysts for Chirally Selective Synthesis of Single Walled Carbon Nanotubes

Electronic and optical properties of single-walled carbon nanotubes (SWCNTs) are correlated with their geometric structures, i.e. chirality index (n,m). Thus, many potential applications require the use of monochiral SWCNTs. Chirally selective synthesis of nanotubes is the ultimate goal in SWCNT production, which
remains a great challenge.In this work, we demonstrated a method to convert three types of Co/SiO₂ catalysts, which are either inactive for the SWCNT growth or only selective to small-diameter nanotubes, into chirally selective catalysts to grow SWCNTs enriched with large-diameter (9,8) tubes (up to 40.5%) by doping catalysts with S. Catalysts were characterized by temperature programmed reduction. Based on experimetnal results, we also proposed in the mechanism that S atoms near Co atoms assist the formation of Co nanoparticles which are selective to (9,8) tubes. Moreover, H⁺ ions may react with CoO_x to form well dispersed Co hydrosilicate and surface Co silicate on SiO2, which increases the selectivity to SWCNTs.

Reference: Chem. Commun., 2013, 49, 2031--2033