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

Abstract

The nitrogen (N)-doped carbon (CNx) nanotubes were synthesized by pyrolysis of ethylenediamine with Ni1·07Mg1·01AlO3·58, Ni1·99Mg0·29AlO3·78, and Ni2·31Mg0·08AlO3·89 mixed oxides as catalysts at 650°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 CN x 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 CN x nanotubes can be controlled to a certain extent by varying the content of Ni2+ in LDH precursors.