Influence of catalyst supporters on catalyst nanoparticles in synthesis of single-walled carbon nanotubes

Abstract

It is important to understand catalytic reactions involved in synthesizing carbon nanotubes. Usually, catalysts are used with supporters for better stability and influences of supporters on catalysis is negligible; however, catalysts used for synthesizing single-walled carbon nanotubes are too small to neglect their influence. Here, we experimentally investigated efficiencies of commonly used catalyst supporters such as magnesium oxide, zeolite, and aluminum oxide when they were combined with iron–cobalt, which is a typical catalyst. It was observed that zeolite-supported catalysts could synthesize single-walled carbon nanotubes, while the others could not. Cluster molecular orbital calculations showed that electronic states of catalysts supported by MgO in the boundary layer between catalysts and supporters were restricted due to covalent bonding between cobalt and magnesium. Density functional theory calculations indicated that catalysts on zeolite had enough electrical orbital near Fermi level and they widely spread over catalysts surface, but catalysts on MgO did not. This characteristic can affect catalytic activities.