Promoted growth of carbon nanotubes by sulfur addition in chemical vapor deposition shown via Arrhenius law

Abstract

We have employed a chemical vapor deposition (CVD) process to grow carbon nanotube (CNT) on a substrate where cobalt and molybdenum binary catalyst system and carbon monoxide were used as a catalyst source and carbon source, respectively. In addition to Co/Mo catalyst, we added sulfur powder into a catalyst layer as a growth promoter. From scanning electron microscopy (SEM) images, production of CNT was enhanced in the presence of sulfur compared with Co/Mo alone even when oxygen was used as one of feed gas. CNT growth rate obeyed Arrhenius equation, showing that the activation energy required for CNT growth was drastically reduced in the use of sulfur. In this study, based on the activation energy in different catalyst conditions, we attempted to consider the rate-controlling step in each case and to interpret the enhancement of CNT synthesis by sulfur addition.