Synthesis and Characterization of Nanoscale Molybdenum Sulfide Catalysts by Controlled Gas Phase Decomposition of Mo(CO)₆and H₂S

Molybdenum sulfide catalysts with surface areas ranging from 16 to 120 m 2 /g were prepared by the thermal decomposition of Mo(CO) 6 and H 2 S vapors in a specially designed tubular reactor system. The gas phase decomposition (GPD) reactions performed at 500−1100 °C produced only MoS 2 when excess H 2 S was used. The optimum temperature range for the high-yield production of MoS 2 was from 500 to 700 °C. By controlling the decomposition temperature, the Mo(CO) 6 partial pressure, or the inert gas flow rate, the surface area, oxidation state, chemical composition, and the grain size of the molybdenum sulfide product(s) were modified. At reactor temperatures between 300 and 400 °C, lower valent molybdenum sulfide materials, which were sulfur deficient relative to MoS 2, were obtained with formal molybdenum oxidation states intermediate to those found for Chevrel phase compounds, M‘Mo 6 S 8 (M‘ = Fe, Ni, Co) and MoS 2 . By lowering the H 2 S flow rate used for the GPD reaction at 1000 °C, mixtures containing variable amounts of MoS 2 and Mo 2 S 3 were produced. Thus, through the modification of critical reactor parameters used for these GPD reactions, fundamental material properties were controlled.