Diameter-Selective Synthesis of Single-Walled Carbon Nanotubes on Supported Cobalt Catalysts
Abstract
Supported Co catalysts were prepared by impregnating the support (MgO, SiO2 and Al2O3) with Co(acac)2 solution, and diameter-selective growth of single-walled carbon nanotubes (SWCNTs) by ethanol chemical vapor deposition has been assessed on these Co catalysts. In contrast to Co/SiO2 and Co/Al2O3 catalysts with relatively high surface areas, Co/MgO catalyst with a low surface area demonstrates the best performances in the diameter-selective growth of SWCNTs under an optimal growth condition. Multiple characterizations on catalysts and SWCNTs revealed that Co(acac)2 was absorbed on MgO by ligand exchange and anhydrous solvent CH2Cl2 strengthened the anchoring of Co(acac)2 on the MgO surface, which resulted in well-dispersed Co species upon calcination in air. Under a modest reduction temperature, the reduction of Co oxides provided Co clusters, which were anchored by the unreacted Co ions in the interior of MgO support, leading to the synthesis of SWCNTs with a narrow diameter distribution.
