Carbon produced by the catalytic decomposition of methane on nickel: Carbon yields and carbon structure as a function of catalyst properties

• Carbon nanotubes are produced by catalytic methane decomposition on nickel.
• The physical characteristics of the nanotubes reflect catalyst properties.
• Alumina and calcium carbonate are much poorer supports for nickel.
• Promotion with copper leads to changes in nanotube morphology.
• The carbon could be used in direct carbon fuel cells.

The interplay of carbon quantity, carbon type, methane decomposition activity and catalyst deactivation by deposited carbon are all important aspects to be considered in assessing the practical use of the catalytic methane decomposition route, using nickel/titania catalysts.Increasing the nickel loading from 7% to 20% in Ni/TiO2 increased methane decomposition conversion but the activities and carbon yields per unit Ni fell as the nickel content increased. The carbon produced on high Ni-loaded samples is more graphitic in nature. Filaments of carbon are the main products and the diameter increases as the Ni particle size on the catalyst increases, which, in turn, increasing at higher Ni loadings. Studies of binary supports on the activity of nickel demonstrated that not all systems led to improved catalyst performance. But, in these systems, factors such as metal-support interaction are also important. Introduction of copper to the supported nickel system exerts an effect on the morphology of the carbon nanostructures produced but other aspects are little affected.