Catalytic synthesis of carbon nanotubes from the decomposition of methane over a Ni–Co/La2O3 catalyst

Abstract

The production of multi-walled carbon nanotubes (MWNTs) by the catalytic chemical vapour deposition (CCVD) method was examined over a series of Ni–Co/La2O3 catalysts with methane as the carbon source. The catalyst composition and the reaction conditions were optimized by analyzing the effluent gas with gas chromatography. Various techniques, such as X-ray diffraction (XRD), Transmission electron microscopy (TEM), Raman spectra, and Thermal gravimetric analysis (TGA) were used to characterize the catalysts and products. The results indicate that the unreduced catalyst 30Ni–10Co/La2O3 showed the highest activity for methane decomposition, and the highest carbon yield, being 624.2%, was obtained over this catalyst at 700 °C after 60 min of reaction with hydrogen as carrier gas. TGA results suggest that the purity of carbon nanotubes (CNTs) can reach up to 98 wt% after a single-step purification by hydrochloric acid.Key words: carbon nanotubes, catalytic chemical vapour deposition, methane decomposition, Ni–Co/La2O3 catalyst.