Probing In Situ Structure-Activity Relationship in 2D Nanoscale MoS₂ Catalysts for Methane-to-Methanol Under High Pressure

Ushering in carbon-neutral energy breakthroughs is critical to reduce greenhouse emissions and achieve clean energy targets. Catalyzing potent greenhouse gases like methane into useful chemicals, such as methanol, is a key reaction to achieve net-zero emissions and meet strict international carbon management goals. Methane-to-methanol (MtM) feed streams often contain contaminants, and MtM processes generally require elevated pressures and strong oxidants to be effective in converting methane. Therefore, resilient catalysts are imperative for creating sustainable processes. Molybdenum disulfide (MoS₂), a transition metal dichalcogenide commonly used in hydrogenation applications, is a low-cost catalyst material with superb durability under the intensive reaction conditions required for MtM. We have studied nanoscale 2D MoS₂ as an MtM catalyst, synthesized <i>via</i> a bottom-up colloidal synthesis approach to yield active edge sites and tight size control of ~5 nm. This colloidal approach affords a uniform distribution of size and morphology, which allows us to clearly relate observed physicochemical features with catalytic function and behavior. Using <i>in situ</i> synchrotron measurements, we probed the local and electronic structure of MoS₂ using pair distribution function and X-ray absorption spectroscopy under high-pressure reaction conditions, giving insight to how these catalysts behave when exposed to different pressures, temperatures, and in the presence of reactants. We observed excellent methane conversion activity in MoS₂ nanosheets, producing methane derivative oxygenates under mild conditions at competitive rates in comparison to precious metal catalysts while maintaining high selectivity. By elucidating these mechanisms through robust multimodal X-ray characterization and kinetic studies in real time, we can better design and optimize MoS₂ for peak methane conversion performance.