Structure and catalytic properties of molybdenum sulfide nanoplatelets

A nanostructured form of molybdenum disulfide/dioxide was prepared by a two-step hydrothermal/gas phase reaction carried at high-temperature sulfidation of molybdenum in H₂S/H₂ for 2 h. The material was composed of a solid MoO₂ core with MoS_2+x crystallites nucleating on its surface. Most of the MoS_2+x have the shape of a single stacked platelet, which are 12-30 nm long and are about one MoS₂ unit cell wide. High-resolution electron microscopy (HREM), energy-dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (STEM), in high-angle annular dark-field (HAADF). Electron diffraction (EDX) in the transmission electron microscope and X-ray diffraction were used to characterize the structure of the catalysts. It is found that the sample consists of MoS_2+x nanoplatelets with unit cell thickness which are exfoliated and are free to rotate along the basal plane. In addition, the edges of the platelets become very rough increasing the number of adsorption sites. The structure-catalytic properties of MoS_2+x for hydrogenation over sulfur removal were observed in the hydrodesulphurization (HDS) reaction of dibenzothiophene (DBT). It was found that nanoplatelets have a very high catalytic activity for HDS. The number of adsorption sites is incremented by the presence of steps and kinks at the edges of the nanoplatelets.