The role of hydrogen in the aerosol-assisted chemical vapor deposition process in producing thin and densely packed vertically aligned carbon nanotubes Original Research Article

Aerosol-assisted catalytic chemical vapor deposition (CCVD) is an efficient single-step process to synthesize vertically aligned carbon nanotube (VACNT) arrays from ferrocene and toluene precursors. While no promoters are needed, adding hydrogen to the carrier gas assists the process. In order to understand the role of hydrogen, we performed syntheses at 850 and 800 °C. The product distribution along the length of the reactor was analyzed by electron microscopy to follow the effect of the hydrogen, as well as the characteristics of the CNT and catalyst nanoparticles. Increasing the hydrogen content shifts the CNT growth towards the furnace entrance and strongly reduces the CNT diameters, while the CNT number density increases. Hydrogen demonstrably affects the gas phase phenomena by lowering the decomposition temperature of ferrocene and increasing the nucleation site density of the catalytic nanoparticles. The yield under hydrogen remains reasonable in the aerosol-assisted CCVD process, and is even improved at 800 °C. Hydrogen content appears to be an interesting parameter to control the characteristics of vertically aligned CNT.