Structure and catalytic properties of hexagonal molybdenum disulfide nanoplates

Abstract

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 Å. 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° and 19° 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.