In situ XAFS study on chemical states of Co and Ir nanoparticles under conventional growth condition of single-walled carbon nanotube via alcohol catalytic chemical vapor deposition

[Display omitted] •In situ XAFS study of single-walled carbon nanotube growth from catalyst particles.•Co catalysts were partially carbonized during nanotube growth.•In contrast, Ir catalysts were metallic during nanotube growth.•In situ XAFS result supported the growth model proposed by a computer simulation. In situ X-ray absorption fine structure (XAFS) analysis was performed on Co and Ir catalysts during single-walled carbon nanotube (SWCNT) growth via alcohol catalytic chemical vapor deposition (Ar/H2 carrier gas). The Co catalysts were partially reduced during heating to 800 °C, and partially carbonized during SWCNT growth upon ethanol addition. The Ir catalysts were reduced during heating and became metallic at 900 °C; the Ir catalysts remained metallic during SWCNT growth upon ethanol addition. The chemical states of the catalyst particles varied with the metal properties during SWCNT growth; thus supporting the growth model proposed using atomistic computer simulations.