Synthesis of nitrogen-doped carbon nanotubes with layered double hydroxides containing iron, cobalt or nickel as catalyst precursors

Nitrogen-doped carbon nanotubes (CN_x) were synthesized by the catalytic chemical vapour deposition of ethylenediamine with layered double hydroxides (LDHs) containing iron, cobalt or nickel as catalyst precursors at 650 °C. The catalytically active metal particles were obtained by calcination of LDHs followed by reduction. X-ray diffraction was used to characterize the structures of the precursors and their calcined products. Transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to characterize the grown CN_x. The results show that the CN_x grown with Mg₂Fe-LDH as catalyst precursor have abamboo-like morphology and large diameter, while hollow tubes are obtained with CoMgAl- and NiMgAl-LDH as catalyst precursors. The CN _x grown with CoMgAl-LDH have the highest N-doped content and the CN_x grown with NiMgAl-LDH have the highest degree of graphitization among these three products.