In recent years, the potential use of hydrogen as a clean energy source has gained considerable attention. Especially H-2 formation by Ni-catalyzed reforming of methane at elevated temperatures is an attractive process. However, a more fundamental knowledge at the atomic level is needed for a full comprehension of the reactions at the catalyst surface. In this contribution, we therefore investigate the H-2 formation after CHx impacts on a Ni(1 1 1) surface in the temperature range 400-1600 K, by means of reactive molecular dynamics (MD) simulations using the ReaxFF potential. While some H-2 formation is already observed at the lower temperatures, substantial H-2 formation is only obtained at elevated temperatures of 1400 K and above. At 1600 K, the H-2 molecules are even the most frequently formed species. In direct correlation with the increasing dehydrogenation at elevated temperatures, an increased surface-to-subsurface C-diffusivity is observed as well. This study highlights the major importance of the temperature on the H-2 formation. (C) 2013 Elsevier B.V. All rights reserved.