Abstract
Multi-walled carbon nanotubes (MWCNTs) were prepared via chemical vapor deposition (CVD) using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs). Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs.
Highlights
Layered double hydroxides (LDHs), variedly known as anionic clays, can be structurally described as stacks of positively charged layers intercalated with anions within its inter-spacing
This study reports the application of three metal-based catalysts; FeCoNiAl-DH, CoNiAl-layered double hydroxides (LDHs), and FeNiAl-LDH for use in the formation of carbon nanotubes (CNT)
The catalytic activity of CoNiAl, FeNiAl and FeCoNiAl mixed oxide catalyst were tested in hexane decomposition at a reaction temperature of 800 °C
Summary
Layered double hydroxides (LDHs), variedly known as anionic clays, can be structurally described as stacks of positively charged layers intercalated with anions within its inter-spacing. Enhanced catalytic activities can be observed by incorporating transition metal cations into the brucite-like layers of LDHs, contributed by the unique properties of the final catalysts, such as high metal dispersion and large surface area after a controlled thermal treatment. The resulting FeCoNiAl, CoNiAl, and FeNiAl composite oxides were obtained by calcination of corresponding LDH precursors at 800 °C, and were used as catalyst or substrate in the formation of carbon nanotubes. The influence of these three types of material towards growth of CNTs was examined and visualized via various means of physiochemical analyses
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