The mechanism for H 2S-CeO 2(111) interactions in solid oxide fuel cells (SOFCs) has been investigated by using periodic density functional theory (DFT) calculations. In order to properly characterize the effect of the localization of Ce 4f states on the interactions, DFT + U calculations were applied. Adsorption of H2S, SH, and atomic S was initially examined to locate energetically favorable intermediates. The species adsorb favorably at the Ce-top, O-top, and Ce-O bridging sites, respectively. Potential energy profiles for the H 2SCeO 2 (111) interactions along the three product channels producing H 2, H 2O, and SO 2 were constructed using the nudged elastic band (NEB) method. Calculations show that H 2S weakly bounds on CeO 2(111) with a small binding energy, followed by dehydrogenation processes, forming surface sulfur species with an exothermicity of 29.9 kcal/mol. Molecular-level calculations demonstrated that the SO 2-forming pathway is energetically most favorable.