Influence of Mo on the Fe:Mo:C nano-catalyst thermodynamics for single-walled carbon nanotube growth

TL;DR

This study investigates how molybdenum (Mo) influences the thermodynamics of Fe:Mo nanocatalysts, revealing that Mo presence enhances catalytic activity and reduces the minimum size for effective single-walled carbon nanotube growth.

Contribution

It provides a detailed ab initio thermodynamic analysis of Fe:Mo catalysts, showing Mo's role in improving nanotube growth conditions and guiding future catalyst design.

Findings

Mo promotes Mo2C nucleation, enhancing catalyst activity.

Mo reduces the minimum particle size for SWCNT growth.

The model explains experimental observations and suggests new catalyst strategies.

Abstract

We explore the role of Mo in Fe:Mo nanocatalyst thermodynamics for low-temperature chemical vapor deposition growth of single walled carbon nanotubes (SWCNTs). By using the size-pressure approximation and ab initio modeling, we prove that for both Fe-rich (~80% Fe or more) and Mo-rich (~50% Mo or more) Fe:Mo clusters, the presence of carbon in the cluster causes nucleation of Mo2C. This enhances the activity of the particle since it releases Fe, which is initially bound in a stable Fe:Mo phase, so that it can catalyze SWCNT growth. Furthermore, the presence of small concentrations of Mo reduce the lower size limit of low-temperature steady-state growth from ~0.58nm for pure Fe particles to ~0.52nm. Our ab initio-thermodynamic modeling explains experimental results and establishes a new direction to search for better catalysts.