Density Functional Theory Calculations of the Dissociation of H 2 on (100) 2H-MoS 2 Surfaces: A Key Step in the Hydroprocessing of Crude Oil

Hydrogen activation on the (100) surface of MoS 2 structures was investigated by means of density functional theory calculations. Linear and quadratic synchronous transit methods with a conjugate gradient refinement of the saddle point were used to localize transition states. The calculations include heterolytic and homolytic dissociation of hydrogen; that is, an H 2 molecule dissociates on an MoS 2 catalyst surface into two hydrogen atoms, which react further with the catalyst surface under formation of either one Mo-H and one S-H (heterolytic) or of two S-H surface groups (homolytic). Our results favor the heterolytic adsorption of hydrogen. Ni- and Co-promoted MoS 2 have been considered to investigate the secondary promotional effect on the H 2 dissociation. The authors observed a negative secondary promotional influence on the H 2 dissociation in the case of Ni-promoted MoS 2 , whereas Co shows a positive effect.