Highly selective growth of (6,5) single-walled carbon nanotubes from sigma phase alloy catalyst

The chirality structure of a single-walled carbon nanotube (SWNT) strongly depends on the composition of catalyst used in the chemical vapor deposition process. In this study, we develop a porous magnesia supported manganese-rhenium (MnRe/MgO) catalyst for chirality-selective synthesis of SWNTs. Detailed characterizations reveal that (6,5) tubes with a selectivity higher than 70% are grown from the Re-rich MnRe/MgO catalyst. By comparing the SWNT growth results with those of monometallic Mn or Re, the formation of sigma phase, an intermetallic compound occurring in transition-metal alloy systems, is revealed to be crucial for the dominant synthesis of (6,5) SWNTs. This work not only extends the application of sigma phase alloy for catalytic synthesis of SWNTs, but also sheds lights on the growth of SWNTs with a high chirality selectivity.