Effect of Fe/Ni catalyst composition on nitrogen doping and field emission properties of carbon nanotubes

Nitrogen-doped carbon (CNx) nanotubes have been synthesized by acetonitrile vapor decomposition over catalyst nanoparticles produced in the result of thermolysis of solid solutions of Fe and Ni bimaleates. X-ray photoelectron spectroscopy revealed the nitrogen content in CNx nanotubes grows from 0.4 to 1.2 at%, when Ni portion in catalyst increases. Nitrogen doping level of sample produced using bimaleates of Fe and Ni taken in a ratio of 7:3 is deviated from this dependence due to formation of two phases of metallic catalyst. N 1s-edge X-ray absorption spectra of samples showed three peaks, which by results of quantum-chemical calculation on nitrogen-containing carbon nanotube (CNT) model were assigned to pyridinic, graphitic, and molecular forms of nitrogen. Measurements of current–voltage characteristics of the samples found the electron emission threshold is reduced with amount of nitrogen incorporated into CNx nanotubes.