Fe-based catalysts from Mg/Fe layered double hydroxides for preparation of N-doped carbon nanotubes

The N-doped carbon nanotubes (CNx) were prepared by catalytic chemical vapor deposition of ethylenediamine with a series of Mg/Fe layered double hydroxides (LDHs) as catalyst precursors. The catalytic actived Fe particles were obtained by calcination of LDHs containing Fe3+ ions followed by reduction. The purification of CNx was carried out using a diluted nitric acid. The obtained products were characterized by X-ray diffraction, inductively coupled plasma spectrum, transmission electron microscope, X-ray photoelectron spectroscopy and Raman spectroscopy. The growth temperature has a distinct effect on the morphology and structure of CNx. Enhancing the growth temperature from 550 °C to 750 °C, the morphology of CNx changes from straight to bamboo-like and to bell-like, whereas the N-doped level decreases from 8.8 to 5.7 at.%. The content of Fe in precursors has little effect on the morphology of CNx, but it affects the N-doped level and structure. These results indicate that the morphology and structure of CNx are related to the synthetic parameters, like the growth temperature and composition of catalyst.