Floating Fe Catalyst Formation and Effects of Hydrogen Environment in the Growth of Carbon Nanotubes

Hydrocarbon conversion to advanced carbon nanomaterials
with concurrent
hydrogen production holds promise for clean energy technologies. This
has been largely enabled by the floating catalyst chemical vapor deposition
(FCCVD) growth of carbon nanotubes (CNTs), where commonly catalytic
iron nanoparticles are formed from ferrocene decomposition. However,
the catalyst formation mechanism and the effect of the chemical environment,
especially hydrogen, remain elusive. Here, by employing atomistic
simulations, we demonstrate how (i) hydrogen accelerates the ferrocene
decomposition and (ii) prevents catalyst encapsulation. A subsequent
catalytic dehydrogenation of methane on a liquid Fe nanoparticle showed
that carbon dimers tend to be the dominant on-surface species. Such
atomistic insights help us better understand the catalyst formation
and CNT nucleation in the early stages of the FCCVD growth process
and optimize it for potential scaleup.