DFT study on the sulfurization mechanism during the desulfurization of H2S on the ZnO desulfurizer

The sulfurization mechanism of H2S on the ZnO(101¯0) surface during the desulfurization of coal gas was investigated by using periodic density functional theory (DFT) calculations. The adsorption of H2S, SH, atomic S, and atomic H, as well as the coadsorption of SH and an H atom, and the coadsorption of S and two H atoms, were initially examined to identify energetically favorable intermediates. Potential energy profiles for three paths of H2S − ZnO(101¯0) interactions producing H2 and H2O were obtained, respectively. Our results show that H2S is preferred to dissociatively adsorb on the ZnO(101¯0) surface, followed by dehydrogenation process to form sulfur species. Molecular-level calculations demonstrate that H2O formation via the H2S−ZnO interaction is the most probable reaction pathway both kinetically and thermodynamically. ZnO has double functions during the desulfurization of H2S. One is as a catalyst to accelerate the dissociation of H2S, while the other is as the reactant participating in the reaction of H2S with ZnO to form H2O.

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► ZnO has two roles (as catalyst and reactant) during the desulfurization of H2S.
► H2S is preferred to dissociatively adsorb on the ZnO(101(—)0) surface.
► The S atom bridging a Zn−O bond is the most stable configuration.
► H2O-forming via H2S-ZnO interaction is the most favorable reaction route.