First principles study of H 2S adsorption and dissociation on Fe(1 1 0)

Abstract

We report first principles density functional theory (DFT) results of H 2S and HS adsorption and dissociation on the Fe(1 1 0) surface. We investigate the site preference of H 2S, HS, and S on Fe(1 1 0). H 2S 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 H 2S, 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 H 2S 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 H 2S 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 H 2S is kinetically and thermodynamically facile.