Controlling pyridinic, pyrrolic, graphitic, and molecular nitrogen in multi-wall carbon nanotubes using precursors with different N/C ratios in aerosol assisted chemical vapor deposition

Abstract

Nitrogen-containing multi-wall carbon nanotubes (N-MWCNTs) were synthesized using aerosol assisted chemical vapor deposition (CVD) techniques in conjunction with benzylamine:ferrocene or acetonitrile: ferrocene mixtures. Different amounts of toluene were added to these mixtures in order to change the N/C ratio of the feedstock. X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy detected pyridinic, pyrrolic, graphitic, and molecular nitrogen forms in the N-MWCNT samples. Analysis of the spectral data indicated that whilst the nature of the nitrogen-containing precursor has little effect on the concentrations of the different forms of nitrogen in N-MWCNTs, the N/C ratio in the feedstock appeared to be the determining factor. When the N/C ratio was lower than ca. 0.01, all four forms existed in equal concentrations, for N/C ratios above 0.01, graphitic and molecular nitrogen were dominant. Furthermore, higher concentrations of pyridinic nitrogen in the outer shells and N 2 molecules in the core of the as-produced N-MWCNTs suggest that the precursors were decomposed into individual atoms, which interacted with the catalyst surface to form CN and NH species or in fact diffused through the bulk of the catalyst particles. These findings are important for a better understanding of possible growth mechanisms for heteroatom-containing carbon nanotubes (CNTs) and therefore paving the way for controlling the spatial distribution of foreign elements in the CNTs using CVD processes.

Electronic Structure of Nitrogen- and Phosphorus-Doped Graphenes Grown by Chemical Vapor Deposition Method

“…A rise of the low-energy component and the high-energy component in the spectrum of the annealed N-graphene supposes the transformation of the pyrrolic N in the pyridinic N and graphitic N, respectively. At the excitation energy of 830 eV, the mean free path of the N 1s photoelectrons allows probing about five graphene layers [51]. Thus, the spectra measured at this energy provide information about nitrogen distributed in all layers of the N-graphene film.…”

Pyrrolic nitrogen-doped multiwall carbon nanotubes using ball-milled slag-SiC mixtures as a catalyst by aerosol assisted chemical vapor deposition

“…Ombaca et al [55] reported that N-pyrrolic configuration in carbon nanotubes improves the palladium catalytic properties because it introduces a better catalytic activity in the carbon material. Bulusheva et al [56] synthesized N-MWCNTs by AACVD method using ferrocene as catalytic precursor and benzylamine or acetonitrile as nitrogen and carbon precursors. Their results revealed that the concentration ratio N/C is determinant for how the nitrogen is incorporated into the lattice of carbon nanotubes.…”

Field emission properties of aligned CNx nanotube arrays synthesized by pyrolysis of a ferrocene/acetonitrile aerosol at different temperatures

“…Since duration of synthesis was the same for all samples, the rate of CN x nanotube growth is influenced by the temperature. The CCVD synthesis of nanotubes includes three stages: (i) decomposition of precursor on a catalytic surface, (ii) diffusion of the cracking products through the bulk and/or subsurface layers of a catalyst, and (iii) precipitation of these species in a tubular form . We conclude that in our synthesis conditions the optimal temperature for these processes is 800–850 °C.…”