To investigate the effect of the catalyst and metal–support interaction on the methane decomposition behavior and physical properties of the produced carbon, catalytic decomposition of methane (CDM) was studied using Ni/SiO2 catalysts with different metal–support interactions (synthesized based on the presence or absence of urea). During catalyst synthesis, the addition of urea led to uniform and stable precipitation of the Ni metal precursor on the SiO2 support to produce Ni-phyllosilicates that enhanced the metal–support interaction. The resulting catalyst upon reduction showed the formation of uniform Ni0 particles (< 10 nm) that were smaller than those of a catalyst prepared using a conventional impregnation method (~ 80 nm). The growth mechanisms of methane-decomposition-derived carbon nanotubes was base growth or tip growth according to the metal–support interaction of the catalysts synthesized with and without urea, respectively. As a result, the catalyst with Ni-phyllosilicates resulting from the addition of urea induced highly dispersed and strongly interacting Ni0 active sites and produced carbon nanotubes with a small and uniform diameter via the base-growth mechanism. Considering the results, such a Ni-phyllosilicate-based catalyst are expected to be suitable for industrial base grown carbon nanotube production and application since as-synthesized carbon nanotubes can be easily harvested and the catalyst can be regenerated without being consumed during carbon nanotube extraction process.

    Abstract
    1 Introduction
    2 Experimental section
        2.1 Catalyst preparation
        2.2 Catalyst characterization
        2.3 Catalyst evaluation
    3 Results and discussion
        3.1 Methane decomposition behavior
        3.2 Properties of CNTs and used catalysts
        3.3 Catalyst morphology
        3.4 Metal–support interaction
        3.5 Relationship between methane decomposition behavior and metal–support interaction
    4 Conclusions
    Acknowledgements 
    References

• Jeong Bin Choi(C1 Gas and Carbon Convergent Research, Korea Research Institute of Chemical Technology (KRICT), Department of Chemical Engineering and Applied Chemistry, Chungnam National University)
• Ji Sun Im(C1 Gas and Carbon Convergent Research, Korea Research Institute of Chemical Technology (KRICT), Advanced Materials and Chemical Engineering, University of Science and Technology (UST))
• Seok Chang Kang(C1 Gas and Carbon Convergent Research, Korea Research Institute of Chemical Technology (KRICT))
• Young‑Seak Lee(Department of Chemical Engineering and Applied Chemistry, Chungnam National University)
• Chul‑Wee Lee(C1 Gas and Carbon Convergent Research, Korea Research Institute of Chemical Technology (KRICT))