| Abstract
| - The present study attempts to examine the relationship between electronic-structure properties exhibited by4d-transition-metal sulfides (TMSs) in connection with the hydrodesulfurization (HDS) catalytic activity.The electronic structure is studied by means of a periodic density functional approach using a plane-wavebasis set and appropriate pseudopotentials. Both bulk and relevant surfaces of NbS, NbS2, MoS2, TcS2, RuS2,Rh2S3, PdS, and PdS2 have been analyzed. High densities of nonbonding states below the Fermi level havebeen found for the TMSs that exhibit good catalytic performance. Therefore, it is suggested that the incompletefilling of the band gap at exposed transition metal atoms over the catalyst surface plays a determinant role inthe HDS reactions. It has also been found that the highest HDS activity occurs when the surface-metal-sitedensity of electronic states has a local minimum at the Fermi level that enhances the donation−back-donationmechanism. Additionally, the Sabatier principle is qualitatively rationalized in terms of the position of covalentbands below the Fermi level.
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