Density Functional Theory Calculations of the Dissociation of H2 on (100) 2H-MoS2 Surfaces: A Key Step in the Hydroprocessing of Crude Oil

Abstract

Hydrogen activation on the (100) surface of MoS2 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 H2 molecule dissociates on an MoS2 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 MoS2 have been considered to investigate the secondary promotional effect on the H2 dissociation. The authors observed a negative secondary promotional influence on the H2 dissociation in the case of Ni-promoted MoS2, whereas Co shows a positive effect.