Atomic-scale insight into adsorption of sterically hindered dibenzothiophenes on MoS2 and Co–Mo–S hydrotreating catalysts

Substoichiometric Molybdenum Sulfide Phases with Catalytically Active Basal Planes

Molybdenum sulfide (MoS₂) is widely recognized for its catalytic activities where the edges of the crystals turn over reactions. Generating sulfur defects on the basal plane of MoS₂ can improve its catalytic activity, but generally, there is a lack of model systems for understanding metal-centered catalysis on the basal planes. Here, we synthesized a new phase of substoichiometric molybdenum sulfide (s-MoS_x) on a sulfur-enriched copper substrate. The basal plane of s-MoS_x contains chemically reactive Mo-rich sites that can undergo dynamic dissociative adsorption/desorption processes with molecular hydrogen, thus demonstrating its usefulness for hydrogen-transfer catalysis. In addition, scanning tunneling microscopy was used to monitor surface-directed Ullmann coupling of 2,8-dibromo-dibenzothiophene molecules on s-MoS_x nanosheets, where the 4-fold symmetric surface sites on s-MoS_x direct C-C coupling to form cyclic tetramers with high selectivity.

Sulfur poisoning of emergent and current electrocatalysts: vulnerability of MoS2, and direct correlation to Pt hydrogen evolution reaction kinetics

The recent surge in interest in the utilisation of transition metal dichalcogenides for the hydrogen evolution reaction (HER), as well as the long-standing problem of sulfur poisoning suffered by the established Pt HER electrocatalyst, motivated us to examine the impacts of sulfur poisoning on both emergent and current electrocatalysts. Through a comparative study between MoS2 and Pt/C on the effects of sulfur poisoning, we demonstrate that MoS2 is not invulnerable to poisoning. Additionally, using X-ray photoelectron spectroscopy, correlations have also been established between the atomic percentages of Pt-S bonds and normalised HER parameters e.g. Tafel slope and potential at -10 mA cm(-2). These findings are of high importance for potential hydrogen evolution catalysis.

Simultaneous tetralin HDA and dibenzothiophene HDS reactions on NiMo bulk sulphide catalysts obtained from mixed oxides

Large selectivity differences were found between supported and unsupported NiMoS catalysts in dibenzothiophene HDS and tetralin HDA.