Zinc Single Atom Confinement Effects on Catalysis in 1T-Phase Molybdenum Disulfide

Active sites are atomic sites within catalysts that drive reactions and are essential for catalysis. Spatially confining guest metals within active site microenvironments has been predicted to improve catalytic activity by altering the electronic states of active sites. Using the hydrogen evolution reaction (HER) as a model reaction, we show that intercalating zinc single atoms between layers of 1T-MoS2 (Zn SAs/1T-MoS2) enhances HER performance by decreasing the overpotential, charge transfer resistance, and kinetic barrier. The confined Zn atoms tetrahedrally coordinate to basal sulfur (S) atoms and expand the interlayer spacing of 1T-MoS2 by ∼3.4%. Under confinement, the Zn SAs donate electrons to coordinated S atoms, which lowers the free energy barrier of H* adsorption-desorption and enhances HER kinetics. In this work, which is applicable to all types of catalytic reactions and layered materials, HER performance is enhanced by controlling the coordination geometry and electronic states of transition metals confined within active-site microenvironments

Terahertz Conductivity of Semiconducting 2H and Metallic 1T Phases of Molybdenum Disulfide

Molybdenum disulfide (MoS2) has been extensively studied in its commonly occurring semiconducting 2H phase. Recent synthetic advances have enabled the bulk synthesis of the catalytically promising metallic 1T phase. However, the conductivity of bulk 1T-MoS2 has not been well characterized to ascertain the carrier transport properties. Terahertz (THz) spectroscopy is an ideal technique for obtaining this crucial information because it is a noncontact method of measuring the conductivity of emerging materials with ultrafast time resolution. This work applies THz spectroscopy to bulk 2H-MoS2 and 1T-MoS2, representing the first application of the technique on the 1T phase, with measurements confirming the semiconducting character of 2H-MoS2 and the metallic character of 1T-MoS2. This study provides new insight into the metallic nature of bulk 1T-MoS2 and a direct comparison to the semiconducting 2H phase that, together with physical characterization to obtain material parameters, are important for optimizing applications in catalysis devices and beyond