The mechanisms of interaction between H2S and Ni- or Cu-based anode surfaces in a solid oxide fuel cell were elucidated by density functional slab model calculations. Two reaction pathways via molecular and dissociative adsorption processes were mapped out following minimum energy paths. The energy for H2S adsorption at the atop site of Ni(1 11) lying parallel to the surface is predicted to be -0.55 eV, while that for the dissociative adsorption is -1.75 eV. In contrast, the formation of initial molecular complexes on a Cu surface is energetically unfavorable (E-ad similar to 0.0 eV), suggesting that Cu is more sulfur-tolerant than Ni. (c) 2006 Elsevier B.V. All rights reserved.