Activity competition of catalysts and supports materials on the growth of carbon nanotubes with ZrO₂/Fe catalyst

Activity competition commonly exist when using multiple catalyst particles for growing carbon nanotubes (CNTs), and the diverse catalysts can compete with the carbon source and affect the growth kinetics and morphology of the nanotubes. However, the existed problem is that whether the support materials themselves also can engage in activity competition with the catalysts, and how this may impact the growth of CNTs. Here, we investigated the influence of hypoactive ZrO₂ support material and hyperactive ZrO₂/Fe catalysts on the growth of CNTs, and the activity competition relationship between the support and the catalysts. ZrO₂/Fe catalysts were prepared via a facile hydrothermal method, and employed both CH₄ and C₂H₅OH as carbon sources for growing CNTs. It is interesting that single-walled carbon nanotubes (SWCNTs) were grown by utilizing CH₄ as carbon source, and multi-walled carbon nanotubes (MWCNTs) were synthesized for the use of C₂H₅OH as carbon source. A combination of experimental data and density functional theory simulations was able to reveal the underlying activity competition mechanism between hyperactive catalysts and hypoactive supports. It would provide new insight into the growth mechanisms of CNTs, and provide new ideas for the rational design and controlled growth of CNTs.