Nickel promoter effect on hydrotreating catalysts structures by means of density functional theory (DFT)

Density functional theory (DFT) calculations have been carried out for a set of 19 triangular Nickel Molybdenum Sulfides (NiMoS) nanoclusters. In this study, the atomic ratio α = Ni/(Ni + Mo) ranging from 0 to 0.5 has been considered together to an Mo28S72H32 initial framework structure where the Mo atoms were isomorphically substituted by Ni atoms. All the nanostructures were completely optimized and their electronic properties analyzed. The optimized nanoclusters conserve most of the aspects of the triangular geometry. However, locally the Ni atoms modify the original octahedral coordination generating geometries like square-planar (SP) configuration and bipyramidal square planar (BSP) configurations. Moreover, the results obtained show that in all cases, a metallic character persists even in non-containing Ni promoter in MoS2 triangular nanocluster. This metallic character could be attributed not only to the Ni inclusion on the cluster, but also to the presence of defects inherent to the cut of the cluster from the perfect crystalline MoS2 sheet.