Catalytic synthesis of nitrogen-doped multi-walled carbon nanotubes using layered double hydroxides as catalyst precursors

The nitrogen (N)-doped carbon (CNx) nanotubes were synthesized by pyrolysis of ethylenediamine with Ni1.07Mg1.01AlO3.58, Ni1.99Mg0.29AlO3.58, and Ni2.31Mg0.08AlO3.89 mixed oxides as catalysts at 650 degrees C. Those mixed oxides were obtained by calcination of corresponding layered double hydroxide precursors (LDHs). Structure and composition of LDHs and mixed oxides were characterized by X-ray diffraction (XRD) and Inductively coupled plasma spectrum. X-ray photoelectron spectroscopy and transmission electron microscope were used to characterize the N content, proportion of pyridine-like N structure and morphology of CNx nanotubes. The results showed that the tubes grown with Ni2.31Mg0.08AlO3.89 as catalysts had more obvious bamboo-like structure, larger diameter than those grown with Ni1.07Mg1.01AlO3.58 and Ni1.99Mg0.29AlO3.78. The N content and proportion of graphitic-like N structures increased with the content of Ni2+ increasing in LDH precursors. The morphology, N content and pyridine-like N structures for CNx nanotubes can be controlled to a certain extent by varying the content of Ni2+ in LDH precursors.