Tuning nitrogen functionalities in catalytically grown nitrogen-containing carbon nanotubes

Abstract

Nitrogen-containing carbon nanotubes (NCNT) were grown from acetonitrile, pyridine or N,N-dimethylformamide over a supported Fe-, Co-or Ni catalyst in the temperature range 823-1123 K. The physico-chemical properties of the obtained NCNT, such as the C/N ratio or the nitrogen type, were related to the synthesis parameters. It was found that the C/N ratio increased with increasing temperature which could be related to the thermodynamic stabilities of the metal-carbides and metal nitrides. Also the type of nitrogen present in the graphene layer changed with increasing temperature from predominantly pyridinic-to quaternary nitrogen. NCNT obtained with the Fe catalyst showed bamboo morphology regardless of the C/N source or growth temperature while straight tubes were obtained with the Co-or Ni catalyst. We propose that this difference in morphology can be explained by the thermodynamic stabilities of the different metal-carbides, leading to a 'pulsating' growth in the case of Fe as opposed to a more continuous growth in the case of Co or Ni.

Nitrogen-doped graphene nanosheets as high efficient catalysts for oxygen reduction reaction

“…Figure 1(b) presents the high resolution XPS of N1s spectrum of the NGNSs, in which the complex XPS N1s spectra could be fitted to four components of the binding energy, namely pyridine-type nitrogen atoms (398.2 eV), pyrrolic-type N doping (399.9 eV), graphite-type nitrogen atoms (401.2 eV), and pyridine N-oxide (402.1 eV), indicating that the nitrogen has been doped in NGNSs with multiple status [19,20]. XPS measurement further reveals the NGNSs have a C/N molar ratio of about 8.2, which is by large identical with the result based on element analysis.…”

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

“…It was shown that the concentration and the type of nitrogen depend on the synthesis temperature, gas flow rate, and nature of the catalyst as well as the type of nitrogen precursor. [14][15][16][17] The most common forms of embedded nitrogen discussed in the literature are graphitic, pyridinic and pyrrolic nitrogen. 1,[18][19][20] Graphitic nitrogen refers to a nitrogen atom with three carbon neighbours in a hexagonal lattice, if the nitrogen is two-fold coordinated similar to that is found in pyridine, it is called pyridinic, and three-fold coordinated nitrogen in a region of defective non-aromatic lattice is associated with pyrrolic nitrogen.…”

Modulation of the textures and chemical nature of C–SiC as the support of Pd for liquid phase hydrogenation

“…It confirms that the incorporation of nitrogen in carbon framework indeed improves the catalytic activity. The presence of lone pair electrons of nitrogen had been reported to improve the basicity [25] and to increase the local electron density of the carbon surface [26], which could modify the metal species. Although the signal/noise ratio in XPS spectra (Fig.…”