The molecular-beam spectrometric technique coupled with tunable synchrotron vacuum ultraviolet photoionization is applied to reveal the catalytic decomposition of methane over Ni-based composites with and without impregnated nano-sized samaria-doped ceria (SDC) particles. It is shown that the coating of SDC nanoparticles not only decreases the decomposition temperature, but also increases the conversion ratio, thus indicating that those impregnated SDC nanoparticles are highly catalytically active for methane decomposition. In addition, C2H4 is observed when the impregnated Ni-SDC composites are used as the catalyst, suggesting that SDC coating also suppresses carbon deposition at the anodes of solid oxide fuel cells. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.