First Principles Study of Low Miller Index RuS₂Surfaces in Hydrotreating Conditions

Abstract

Density functional theory (DFT) calculations combined with surface thermodynamic arguments and the Gibbs-Curie-Wulff equilibrium morphology formalism have been employed to explore the effect of the reaction conditions, temperature (T), and gas-phase partial pressures (p H 2 and p H 2 S ) on the stability of low Miller index ruthenium sulfide (RuS 2 ) surfaces. The calculated thermodynamic surface stabilities and the resulting equilibrium morphology models suggest that unsupported RuS 2 nanoparticles in HDS conditions are like to a polyhedron with six, eight, and twelve (100), (111), and (102) faces, respectively. The area of these faces covers about 40%, 37%, and 23% of the total particle, respectively. The atomic basins of the outermost individual atoms of the exposed surfaces were determined using the quantum theory of atoms in molecules methodology. Direct visualization of these basins has shown that a hole just at the middle of the outermost sulfur basins provides access to uncovered metal sites. Analysis of the electrostatic potential mapped onto a selected electron density isocontour (0.001 au) on the exposed surface reveals a very high potential reactivity of these holes toward electrodonating reagents. Consequently, the high attraction between these uncovered sites and S atoms coming from reagent polluting molecules makes these kinds of particles quite active for HDS catalysis.

Guided ion beam and theoretical studies of the reaction of Ru+ with CS2 in the gas-phase: thermochemistry of RuC+, RuS+, and RuCS+

“…[6][7][8][9][10] A density functional study of the low Miller index RuS 2 surfaces under hydrotreating conditions reveals a very high Lewis acidity of accessible metallic ruthenium surface sites. 11 These sites are likely to attract S-atoms, explaining the high HDS reactivity of RuS 2 nanoparticles. In a model system for these surface sites, RuS 2 nanoislands grown on a reconstructed Au (111) surface under ultra-high-vacuum conditions were found to exhibit sulfur vacancies in the RuS 2 (111) plane.…”

RuS2thin films as oxygen-evolving electrocatalyst: Highly oriented growth on single-crystal FeS2substrate and their properties compared to polycrystalline layers

“…Sulphur surface defects were not found as the only factor for the reactivity, but are expected to improve it. Aray et al calculated the surface stability of low Miller index facetted RuS 2 particles by DFT calculations combined with surface thermodynamic considerations. Naked RuS 2 nanoparticles are likely to form polyhedra consisting of (100), (111), and (210) facets with a surface ratio of 40:37:23.…”

Nature of the Active Sites of Molybdenum-Based Catalysts and Their Interaction with Sulfur- and Nitrogen-Containing Molecules Using the Quantum Theory of Atoms in Molecules and the Molecular Electrostatic Potential

“…It is established that cobalt (or nickel) atoms replace the edge molybdenum atoms completely or partially on the sulfur edge first and then the metal edge leading to a CoMoS or NiMoS phase. − Similar studies on RuS 2 nanoclusters using STM , and theoretical calculations , on periodic surface models have suggested that the (111) plane is responsible for the RuS 2 catalytic activity . The STM studies have demonstrated the formation on Au(111) substrate of hexagonal flat RuS 2 islands with an area of 30 nm 2 . In contrast to the MoS 2 nanoclusters, a high density of sulfur vacancy is present on the flat (111) surface of the RuS 2 nanostructures. ,− A large second breakthrough in the structural studies of the active nanostructures in HDS, using the combination of STM and DFT methodologies, has been achieved.…”

“…26 The STM studies have demonstrated the formation on Au(111) substrate of hexagonal flat RuS 2 islands with an area of 30 nm 2 . 26 In contrast to the MoS 2 nanoclusters, a high density of sulfur vacancy is present on the flat (111) surface of the RuS 2 nanostructures. 26,35−39 A large second breakthrough in the structural studies of the active nanostructures in HDS, using the combination of STM and DFT methodologies, has been achieved.…”

“…In HDS processes, organosulfur molecules are removed from oil by reacting with hydrogen to form H 2 S and hydrocarbons. − For second- (4d) and third-row (5d) transition metals, a typical volcano-type connection of the activity of the metal as a function of its position in the periodic table was found. , The first-row (3d) TMS are much less active. RuS 2 , OsS 2 , NiMoS, CoMoS, and Rh 2 S 3 are at the maximum of the volcano, whereas Ni 3 S 2 and MoS 2 are among the less-active sulfides. , The active site’s nature was showed to be intimately related to the metal–sulfur bond strength. − Thus, it was found that the experimental HDS , activities of the entire TMS series, A TMS , following the Sabatier principle, fit on a single volcano master curve when plotted against their bulk cohesive energy per metal–sulfur bond, E (MS) . A first breakthrough was the finding of the synergism effect of Co and Ni atoms on the MoS 2 catalysts.…”