Catalytic Decomposition of Methane to Carbon Nanotubes and Hydrogen: The Effect of Metal Loading on the Activity of CoO-MoO/Al₂O₃ Catalyst

Abstract

The effect of metal loading on the decomposition of methane to carbon nanotubes (CNTs) and hydrogen was studied. The catalysts used were CoO-MoO/Al₂O₃ with the loadings of CoO-MoO ranged from 10 to 40wt%. The catalytic activity of the catalysts in methane decomposition was examined at 700^oC for 2 hours in a horizontal quartz tube reactor. The findings show that an increasing in the metal loading increased the carbon yield and broadened the diameter distribution of the as-produced CNTs, but too much of an increase of metal loading retarded the carbon yield. The highest carbon yield was recorded for the catalyst with 30wt% metal loading. The catalytic activity can be related to the cobalt oxide crystallite size. High-resolution transmission electron microscopy (HRTEM) observation showed that the produced CNTs possessed highly graphitized wall structure that composed of parallel graphene layers and were grown followed the base-growth mechanism. In additional, CO₂-free hydrogen was produced simultaneously with CNTs from the decomposition of methane.

Keywords:

• Carbon nanotubes
• decomposition of methane
• metal loadings
• hydrogen
• high resolution transmission electron microscopy

Acknowledgments

The authors gratefully acknowledge the financial support provided by the Universiti Sains Malaysia under the Research University Grant Scheme (Project A/C No. 814004), USM-RU-PRGS (Project A/C No. 8032038) and the Malaysian Technology Development Corporation (MTDC) under the Commercialization of Research & Development Fund (CRDF) (MBF065- USM/05). The authors would also like to thank Prof. Seiji Takeda and Prof. Tadashi Itoh from Osaka University for allowing the authors to use their HRTEM.