The effect of temperature on the morphology and chemical surface properties of nitrogen-doped carbon nanotubes

One of the most effective ways to tune the physical and chemical properties of CNTs is to dope them with a foreign element, such as nitrogen. Nitrogen atoms that are incorporated into the CNT structure can drastically change the properties of CNTs. The properties of nitrogen-doped carbon nanotubes (N-CNTs) originate from their structure; thus, it is practical to create a desired structure during synthesis. We have investigated the effects of synthesis parameters, mainly temperature, on various characterizations of N-CNTs, such as their morphologies, dimensions (diameter and length), defects, nitrogen inclusions and thermal stability. The results revealed strong correlations between the synthesis parameters and the properties of the synthesized N-CNTs. XPS characterization indicated that the percentage of nitrogen inclusion decreased with increasing synthesis temperature up to 850 °C and then increased at 950 °C. Raman spectroscopy showed a decrease in the number of defects in the N-CNT structure with increasing synthesis temperature. Finally TGA demonstrated a trend of increasing thermal stability of N-CNTs with increasing synthesis temperature, up to 850 °C then a reduced thermal stability at 950 °C. Based on these results, one can control the properties of N-CNTs and obtain materials with the desired characteristics by choosing the appropriate synthesis conditions.