Hydrogen physisorption based on the dissociative hydrogen chemisorption at the sulphur vacancy of MoS2 surface

We provide a new insight that the sulphur-depleted MoS2 surface can store hydrogen gas at room temperature. Our findings reveal that the sulphur-vacancy defects preferentially serve as active sites for both hydrogen chemisorption and physisorption. Unexpectedly the sulphur vacancy instantly dissociates the H-2 molecules and strongly binds the split hydrogen at the exposed Mo atoms. Thereon the additional H-2 molecule is adsorbed with enabling more hydrogen physisorption on the top sites around the sulphur vacancy. Furthermore, the increase of the sulphur vacancy on the MoS2 surface further activates the dissociative hydrogen chemisorption than the H-2 physisorption

The role of cobalt and nickel in hydrodesulfurization : promoters or catalysts?

No abstract

Carbon-supported sulfide catalysts

The activities of sulfided Mo/C, W/C, Co/C, Ni/C, Co-Mo/C, and Ni-W/C catalysts for thiophene hydrodesulfurization and butene hydrogenation were studied using a flow microreactor operating at atmospheric pressure. The following parameters were varied: type of carbon support, carbon pretreatment, catalyst preparation method, and content of active material. The results are compared with those obtained for series of sulfided Mo/¿-Al2O3, W/¿-Al2O3, Mo/SiO2, and W/SiO2. Some samples, viz., Mo/C, Co/C, and Co-Mo/C, were also studied by X-ray photoelectron spectroscopy (XPS). The carbon-supported catalysts demonstrated outstanding performance for thiophene hydrodesulfurization. XPS analysis showed the presence of low-valence-state sulfur, e.g., S- or (S-S)2-, in Mo/C and Co/C catalysts with low molybdenum or cobalt content. These sulfurspecies are supposedly connected with the catalytic activity for hydrodesulfurization. Co/C and Ni/C were found to have a hydrodesulfurization activity which was higher (Co) or the same (Ni) as that measured for Mo/C or W/C. Therefore Co (Ni) ions in Co (Ni)-Mo (W)/C catalysts are considered as promoters for the MoS2 (WS2) phase (low Co/Mo or Ni/W ratios) or as additional active species