Nickel Cobalt Thiospinel Nanoparticles as Hydrodesulfurization Catalysts: Importance of Cation Position, Structural...

First-row transition metal-based thiospinels are prepared via a one-pot versatile strategy and for the first time investigated as hydrodesulfurization (HDS) catalysts. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy analysis confirm that these thiospinels consist of agglomerated nanoparticles (NPs) and contain multivalent metal cations. Among the sulfides synthesized at 230 °C, NiCo₂S₄ presents the highest thiophene conversion. This high intrinsic activity is found to be correlated with the normal spinel structure with Ni cations located on the tetrahedral sites and Co cations on the octahedral sites. However, the spent NiCo₂S₄ NPs experience phase transformation because of the relatively low synthetic temperature. Accordingly, six NiCo₂S₄ samples are prepared in the temperature range of 180-350 °C, and their HDS activity increases monotonically with the synthetic temperature, which is attributed to the higher structural stability and more surface sulfur vacancy of the NiCo₂S₄ NPs prepared at higher temperatures. Notably, the NiCo₂S₄ NPs synthesized at 350 °C exhibit a much higher thiophene conversation of 62.9% than the classic MoS₂ catalyst (39.3%) as well as excellent reusability. Our study suggests that the NiCo₂S₄ thiospinels with high activity and stability can represent a new promising class of industrial HDS catalysts.