FeTiO based catalyst for large-chiral-angle single-walled carbon nanotube growth

Catalyst selection is very crucial for controlled growth of single-walled carbon nanotubes (SWNTs). Here we introduce a well-designed [Formula presented] solid solution for SWNT growth with a high preference to large chiral angles. The [Formula presented] catalyst was prepared by combining Ti layer deposition onto premade Fe nanoparticles with subsequent high-temperature air calcination, which favours the formation of a homogeneous [Formula presented] solid solution. Using CO as the carbon feedstock, chemical vapour deposition growth of SWNTs at 800 °C was demonstrated on the [Formula presented] catalyst. Nanobeam electron diffraction characterization on a number of individual SWNTs revealed that more than 94% of SWNTs have chiral angles larger than 15°. In situ environmental transmission electron microscopy study was carried out to reveal the catalyst dynamics upon reduction. Our results identify that the phase segregation through reducing [Formula presented] catalyst leads to the formation of TiO_x-supported small Fe nanoparticles for SWNT growth. The strong metal-support interactions induced by partial reduction of TiO_x support promote the wettability of Fe nanoparticle, accounting for the preferential growth of large-chiral-angle SWNTs. This work opens a new avenue for chiral angle selective growth of SWNTs.