High-yield production of large aspect ratio carbon nanotubes via catalytic pyrolysis of cheap coal tar pitch

Multi-wall carbon nanotube (MWCNT) with large aspect ratio was prepared on a large scale via Co-catalyzed pyrolysis of cheap pitch at 973-1273 K in Ar atmosphere. The optimal catalyst-content and temperature for growing CNT was 1173 K and 0.75 wt% Co, respectively. The schematic of the formation of MWCNTs can be shown as follows:(a) Co(NO3)2 gradually decomposed to cobalt (Ⅱ) starting at about 473 K;(b) pitch decomposed and released considerable amounts of C2H4 gas;(c) the subsequent separations of C-H and C=C bonds in C2H4;(d) MWCNTs grew from/on the Co cluster via diffusion-penetration.Density functional theory (DFT) calculations suggest that Co catalysts facilitate the CNTs growth by donating electrons from Co atoms to C2H4 molecules, which facilitated the dissociation of the C=C and the C-H bonds.192