First principle calculations of hydrogen sulfide adsorption and dissociation on pure Pd (111) and Au (111), and alloy Pd/Au (111) and Au/Pd (111) surfaces

The hydrogen sulfide adsorption and dissociation on pure Pd (111) and Au (111), alloy Pd/Au (111) and Au/Pd (111) surfaces have been investigated using the pseudo-potential plane wave method within the generalized-gradient approximation density functional theory (GGA_DFT). The results show that H2S tends to be adsorbed on top site, HS prefers to locate on bridge site, and the S and H locate on fcc site on various surfaces. Compared the adsorption of sulfur-containing species and hydrogen on pure and alloy metal surfaces, a similar trend of adsorption energies on the metal surfaces (Pd/Au (111)>Pd (111)>Au (111)>Au/Pd (111)) is found. In addition, the dissociation process on the Pd (111) and Pd/Au (111) surfaces is predicted to be exothermic. However, on Au (111) and Au/Pd (111), the dissociation process is endothermic. The work reveals that H2S dissociation is more likely to happen on Pd/Au (111) surface. Finally, the adsorption energies of adsorbate on metal surfaces have strong correlation with the d-band center. The d-band center moves away from the Fermi level, and the adsorption energy decreases. According to the LDOS analysis, the inner Au atoms of Pd/Au (111) can enhance the top-layer d-band intensity, whereas the inner Pd atoms of Au/Pd (111) cause the opposite effect. The further electronic state analysis reveals the interaction between H2S and metal surfaces.