Synthesis of carbon nanotubes by selective reduction of mixed oxides

Synthesis of carbon nanotubes was carried out over in-situ reduced mixed oxides catalysts containing Ni, Co or Fe prepared from layered double hydroxides (LDHs) precursors. These precursors, including NiMg₂Al-LDHs, CoMg₂Al-LDHs and Mg₃Fe-LDHs with similar transition metal content, have been prepared by coprecipitation, then thermally decomposed to obtain Ni/Mg/ Al, Co/Mg/Al and Mg/Fe mixed oxides. Carbon nanotubes grown on the surface of these mixed oxides have good quality with quite well-turbostratic walls. They have a high aspect ratio and appear to be flexible. Ni/Mg/Al mixed oxides showed the highest catalytic activity. Co/Mg/Al mixed oxides produced carbon nanotubes with the smallest diameter.