Role of Hydrogen in Ethylene-Based Synthesis of Single-Walled Carbon Nanotubes

We examined the effect of hydrogen on the growth of single-walled carbon nanotubes in the aerosol (a specific case of the floating catalyst) chemical vapor deposition process using ethylene as a carbon source and ferrocene as a precursor for a Fe-based catalyst. With a comprehensive set of physical methods (UV-vis-NIR and Raman spectroscopies, transmission electron microscopy, scanning electron microscopy, differential mobility analysis, and four-probe sheet resistance measurements), we showed hydrogen to inhibit ethylene pyrolysis extending the window of synthesis parameters. Moreover, the detailed study at different temperatures allowed us to distinguish three different regimes for the hydrogen effect: pyrolysis suppression at low concentrations (I) followed by surface cleaning/activation promotion (II), and surface blockage/nanotube etching (III) at the highest concentrations. We believe that such a detailed study will help to reveal the complex role of hydrogen and contribute toward the synthesis of single-walled carbon nanotubes with detailed characteristics.

Automated summary

In this study, the effect of hydrogen on the growth of single-walled carbon nanotubes in the aerosol chemical vapor deposition process was investigated. It was shown that hydrogen inhibits the pyrolysis of ethylene, extending the synthesis parameter window. Three different regimes of hydrogen effect were distinguished: pyrolysis suppression at low concentrations, surface cleaning/activation promotion, and surface blockage/nanotube etching at high concentrations. This detailed study contributes to understanding the complex role of hydrogen and its impact on the synthesis of single-walled carbon nanotubes.