Influence of one-pot and two-step preparation on the quality of carbon nanotubes using pine sawdust as the catalyst support

In this paper, a novel low-cost process for preparing carbon nanotubes (CNTs) by loading transition metals (Fe, Co, Ni) on carbon materials (pine sawdust) is investigated. Among three metal catalysts, nickel catalyst exhibits the best catalytic performance including the highest carbon yield (23.8 wt%) and the best quality of the grown CNTs (ID/IG = 1.01). Meanwhile, the nickel content of 2.5 wt% was confirmed to be the most suitable metal content for CNTs growth. Based on the prepared CNTs with pine sawdust as the catalyst support, the two-step method and the one-pot method were proposed. In the two-step method, the Ca(OH)2 powder as a reactive assistant and the introduction of CO2 can obtain CNTs with the least defects and the highest purity. The comparative experiments show that the mere introduction of CO2 without any reactive assistants will cause greater damage to CNTs. In the one-pot method, the addition of Ca(OH)2 improves the quality and thermal stability of CNTs, which verifies the feasibility of the one-pot method reported in this study.