Reaction kinetics in the synthesis of highly nitrogen doped carbon nanotubes

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Matthew Craps (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Daniel Herr

Abstract: Nitrogen doped carbon nanotubes (NCNTs) consist of bamboo structure CNTs with nitrogen atoms in situ doped into the CNT lattice. In this research, NCNTs were synthesized via CVD using ferrocene and pyridine precursors in a pure NH3 environment. To understand the kinetics of nitrogen incorporation in carbon nanotubes, I performed time and temperature evolution studies and logged the mass of NCNT product collected from each run. SEM and TEM visualized the structural changes to the NCNTs, and helped to quantify lengths and diameters. We used XPS to detect the atomic percent nitrogen changes in the nanotubes during growth. The data helped to determine the kinetics of the NCNT growth process. Unexpectedly, two competing mechanisms became apparent at temperatures above 775°C. The percent nitrogen detected by XPS shows a significant drop at 825°C and 850°C relative to the syntheses at 800°C and below. The total mass of NCNT product started decreasing at 800°C and continued decreasing at an increasingly faster rate as temperatures increased. This result caused us to reevaluate our hypotheses and develop some new hypotheses and tests. We proposed a de-doping mechanism, created a de-doping test, and evaluated the percent nitrogen removed at different temperatures, and the types of nitrogen species lost from the lattice. We considered several rate limiting processes and observed specific nitrogen species from the in situ synthesis of NCNTs, as detected by XPS.

Additional Information

Language: English
Date: 2020
Carbon Nanotubes, Catalyst, Kinetics, NCNT, Nitrogen, Synthesis
Chemical kinetics
Carbon nanotubes

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