First principles study of H2S adsorption and dissociation on Fe(1 1 0)

We report first principles density functional theory (DFT) results of H2S and HS adsorption and dissociation on the Fe(1 1 0) surface. We investigate the site preference of H2S, HS, and S on Fe(1 1 0). H2S is found to weakly adsorb on either the short bridge (SB) or long bridge (LB) site of Fe(1 1 0), with a binding energy of no more than 0.50 eV. The diffusion barrier from the LB site to the SB site is found to be small (∼0.10 eV). By contrast to H2S, HS is predicted to be strongly chemisorbed on Fe(1 1 0), with the S atom in the LB site and the HS bond oriented perpendicular to the surface. Isolated S atoms also are predicted to bind strongly to the LB sites of Fe(1 1 0), where the SB is found to be a transition state for S surface hopping between neighboring LB sites. The minimum energy paths for H2S and HS dehydrogenation involve rotating an H atom towards a nearby surface Fe atom, with the S–H bonds breaking on the top of one Fe atom. The barrier to break the first S–H bond in H2S is low at 0.10 eV, and breaking the second S–H bond is barrierless, suggesting deposition of S on Fe(1 1 0) via H2S is kinetically and thermodynamically facile.