The effectiveness of combining one metal of group VI (25% of Cr, Mo or W) to 25% Co supported on MgO has been investigated for catalytic decomposition of methane to COx free hydrogen and carbon nanotubes. The fresh and used catalysts were characterized by XRD, TPR, TEM, Raman spectroscopy, BET and TGA. The results reveal that the addition of group VI metals induce strong interaction with the structural MgO and CoOx crystals associated with enhancement of the surface properties. Also, incorporation of Mo or W metals in Co/MgO enhances the catalytic decomposition stability of methane for long reaction times. This can be attributed to the higher dispersion and stabilization of Co particles via formation of CoMO4 and CoWO4 species. The as-grown carbon material over all catalysts is found to be multi-walled nanotubes as shown in TEM images and Raman spectra. TGA showed that the Co-Mo/MgO catalyst exhibited higher CNT yield. (c) 2014 Elsevier Ltd. All rights reserved.