Bimetallic mesoporous materials for high yield synthesis of carbon nanotubes by chemical vapour deposition techniques

Abstract

Mesoporous Fe-MCM-41, Zn-MCM-41 and Fe–Zn-MCM-41 molecular sieves were synthesized in various Si/metal ratios by the hydrothermal method. The synthesized materials were characterized by various physicochemical techniques such as XRD, N 2 adsorption–desorption isotherm, TGA, DRS-UV spectroscopy, SEM and TEM. The catalytic activity of monometallic Fe-MCM-41, Zn-MCM-41 and bimetallic Fe–Zn-MCM-41 molecular sieves was tested and optimized for the maximum yield of carbon nanotubes (CNTs) by decomposition of acetylene (C 2H 2) at 700–900 °C. The deposited carbon materials were purified and characterized by XRD, SEM, TEM and Raman spectroscopy techniques. The purified samples show the presence of well-graphitized SWNTs over the bimetallic Fe–Zn-MCM-41 (3:1) molecular sieve. It was found that Fe–Zn-MCM-41 in the ratio of 3:1 (Fe:Zn) contains an optimum amount of metal to form metallic clusters, which in turn leads to the formation of CNTs with higher carbon deposition. The diameters of the carbon nanotubes are in the range of 1.2–2.5 nm, which was revealed by the Raman spectroscopy. This study shows that the bimetallic Fe–Zn-MCM-41 mesoporous molecular sieve as a promising catalytic template with good thermal stability and high productivity for the synthesis of CNTs.