The effect of energetic activation of methane and ethane using molecular-beam techniques in their oxidation with 02 under steady-state condition was investigated over Pt and Rh foils. Energetic activation of methane and ethane by heating and seeding promoted the catalytic partial oxidation and enhanced hydrogen formation in particular. Based on the results on the reaction order measurements over Pt foil, one possible explanation for the promotion is that the energetically activated methane and ethane react with adsorbed oxygen and produce methoxy and ethoxy species, which are regarded as precursors for hydrogen formation. The production rates over Rh foil were smaller then over Pt foil, and lower 02 partial pressure was required to produce CO and hydrogen, which is related to the higher oxygen affinity of Rh. (c) 2007 Elsevier B.V. All rights reserved.