Multi-walled carbon nanotubes were synthesized by the catalytic decomposition of acetylene at 750oC over sepiolite powder, which was treated with aqueous cobalt nitrate. It is expected that the composite with high specific area will have high capacity of hydrogen storage. Multi-walled carbon nanotubes were synthesized by the catalytic decomposition of acetylene at 750oC over sepiolite powder, which was treated with aqueous cobalt nitrate. It is expected that the composite with high specific area will have high capacity of hydrogen storage.