Thermal decomposition of nickel acetate (T > 300 degrees C) dispersed on either silica or cordierite supports resulted in a mixture of Ni-0/NiO that was catalytically active for the decomposition of methane to produce CO-free hydrogen, without the need for any pretreatment (i.e., using H-2 at high temperature (> 500 degrees C) for at least 2 h). The carbon yield (g(C)/g(Ni)) for the catalysts supported on SiO2 (similar to 200-300 m(2)/g) increased with an increase in the catalyst NiO mean crystallite size. XRD and FE-SEM studies confirmed the formation of graphitic-type carbon filaments during the methane decomposition. (c) 2005 Elsevier Inc. All riehts reserved.