Structure and catalytic properties of hexagonal molybdenum disulfide nanoplates

Molybdenum disulfide (MoS2) is a compound very useful for its properties; it is used as a lubricant, catalyst in hydrodesulfurization, in hydrogen fuel storage, etc. In this work MoS2 hexagonal nanoplates were synthesized at different temperatures and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). These nanoplates have a size of 25-35 nm as revealed by SEM. With aberration corrected STEM it was possible to measure the interatomic distance of Mo-Mo, which was found to be 2.8 angstrom. The catalytic properties of the nanoplates were measured in the hydrodesulfurization of dibenzothiophene, showing high activity and high direct desulfurization pathway (DDS) selectivity for an unpromoted MoS2 catalyst. Theoretical calculations were performed in 2H-MoS2 as well as 2H-MoS2 with a rotation of 16 degrees and 19 degrees which was applied to the two S planes in the crystalline structure. The results obtained on the rotated 2H-MoS2 yielded indication of a small gap semiconductor of E-g = 0.38 eV when compared to the unrotated 2H-MoS2, which is a semiconductor of E-g = 2.00 eV. This tendency of the rotated crystalline 2H-MoS2 toward metallicity could be responsible for the enhancement of the catalytic properties observed in the material in question, compared to other MoS2-based catalysts.