Selective synthesis of single-walled carbon nanotubes on Fe–MgO catalyst by chemical vapor deposition of methane

• SWCNTs of high yield and selectivity were obtained on 2 wt.% Fe–MgO catalyst.
• High dispersion of Fe species on MgO favors high SWCNT yield and selectivity.
• Carbon yield increased from 850 to 900 °C, SWCNT selectivity decreased above 850 °C.
• Catalyst pretreatment conditions influence catalyst activity and SWCNT selectivity.
• A simple CCVD protocol highly effective to produce high quality SWCNTs is reported.

The selective synthesis of single-walled carbon nanotubes (SWCNTs) with narrow chirality and diameter distribution by methane decomposition over Fe–MgO catalyst is reported. The catalyst was examined by nitrogen physisorption, X-ray diffraction, temperature programmed reduction, X-ray photoelectron spectroscopy, and UV–Vis diffuse reflectance spectroscopy to elucidate the structure and chemical state of the species responsible for SWCNT growth. High resolution electron microscopy, Raman and optical absorption spectroscopy, temperature programmed oxidation, energy dispersive X-ray spectroscopy and nitrogen physisorption were used to probe reaction selectivity, SWCNT chirality and diameter distribution, carbon yield and effectiveness of purification protocols. The yield of carbon increased with an increase in temperature, although SWCNTs selectivity decreased above the optimum synthesis temperature. Results established a clear link between the degree of dispersion of iron oxide species inside the MgO lattice and the catalyst selectivity for SWCNT growth.

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