(509cb) Structural Design of MoS2 Nanosheets with Single Atom Dopants As Efficient Catalysts for Hydrotreating

Tailoring highly efficient catalysts is of utmost importance to reduce the carbon and energy footprints of industrial processes. An important class of industrial chemistries is hydrotreating whereby heteroatoms such as sulfur, oxygen, and nitrogen in carbon-containing feedstocks (hydrocarbons and biomass) are removed catalytically using molecular hydrogen. Transition metal dichalcogenides, such as molybdenum sulfide (MoS₂), have been employed in bulk form commercially as hydrodesulfurization catalysts due to their widespread availability. In the nanoscale, MoS₂ forms stable two-dimensional nanosheets, which exhibit impressive catalytic activity along the nanosheet edge sites. Conversely, the non-edge atoms of the basal plane are sufficiently coordinated and thus relatively inert. Given that a large portion of the surface area is inactive, there is a strong impetus towards modifying and nanostructuring 2D materials to activate the basal plane, such as through decorating the surface with singular dopant atoms to create isolated single-atom active sites that may possess novel catalytic properties for hydrogenation/hydrogenolysis chemistries. Here, we demonstrate the controlled, tunable in-situ cobalt doping of MoS2 nanosheets grown via colloidal hot-injection method. A set of catalysts with various cobalt loadings were studied for hydrodesulfurization of thiophene, specifically probing the effects of dopant concentration and local structure of single cobalt atoms, inferred from x-ray absorption spectroscopy and density functional theory (DFT), on catalytic activity. We demonstrate that the relationship between dopant concentration and thiophene conversion is non-linear, and an optimal cobalt loading exists for efficient sulfur removal.