Catalytic decomposition of methane to COx-free hydrogen and carbon nanotubes over Co–W/MgO catalysts

Bimetallic catalysts containing a series of Co/W at 40/10, 30/20, 20/30 and 10/40 wt% supported on MgO with a total metal content of 50 wt% were prepared and used for the catalytic decomposition of methane to CO_x-free hydrogen and multi-walled carbon nanotubes (MWCNTs). The solid fresh and exhausted catalysts were characterized structurally and chemically through XRD, TPR, BET, TGA, TEM and Raman spectroscopy. The 40%Co–10%W/MgO catalyst exhibited the highest activity for the production of both hydrogen and MWCNTs. The formation of a large amount of non-interacted Co₃O₄ species is considered as the main reason for the catalyst superiority in its activity. On the contrary, catalysts formulations of 20%Co–30%W and 10%Co–40%W demonstrated the formation of a large amount of hardly reducible CoWO₄ and MgWO₄ particles causing lower activity of these catalysts toward methane decomposition as evidenced through the XRD and TPR results.