Steven Farrell1,Ingrid Paredes1,Srinivas Rangarajan2,Anatoly Frenkel3,4,Ayaskanta Sahu1
New York University1,Lehigh University2,Stony Brook University, The State University of New York3,Brookhaven National Laboratory4
Steven Farrell1,Ingrid Paredes1,Srinivas Rangarajan2,Anatoly Frenkel3,4,Ayaskanta Sahu1
New York University1,Lehigh University2,Stony Brook University, The State University of New York3,Brookhaven National Laboratory4
Tailoring highly efficient catalysts to targeted applications is vital to reduce the carbon footprints of industrial processes; however, understanding and controlling nanostructure influence in catalyst design has proven difficult. Transition metal dichalcogenides, such as molybdenum sulfide (MoS<sub>2</sub>), are important commercial catalysts employed in hydrodesulfurization (HDS) and hydrodeoxygenation (HDO) for crude oil and biomass valorization, respectively, due to their widespread availability and sulfur poisoning resistance. Nanoscale MoS<sub>2</sub> forms stable two-dimensional nanosheets with impressive catalytic activity along the nanosheet edge sites. Conversely, most of the non-edge atoms of the basal plane are inert. Thus, there is a strong impetus towards modifying 2D MoS<sub>2</sub> to activate the basal plane. Decorating the surface with singular dopant atoms, such as cobalt, has been shown to enhance catalytic properties of MoS<sub>2</sub> for hydrogenation, especially hydrotreating. However, little is understood about the location of the dopants and their subsequent influence on catalyst behavior. To investigate this gap in knowledge, we study the impact of Co-dopants in MoS<sub>2</sub> on hydrotreating reactions through strictly controlled, tunable in-situ Co doping of MoS<sub>2</sub> nanosheets grown via a bottom–up colloidal hot-injection method. Various Co loadings were studied for HDS of thiophene and HDO of p-cresol, probing the effects of dopant concentration and local structure of single Co atoms using x-ray absorption spectroscopy and density functional theory. We show that the relationship between dopant concentration, location and activity is interrelated, reaction-specific, and non-monotonous with performance peaking at 25% Co. We highlight the specific mechanisms that dictate how and where Co attaches to the surface and its influence on the catalytic performance. Understanding these mechanisms is critical for tailoring future catalysts to specific applications.