Studies of the structure of molybdenum oxide and sulfide supported on thin films of alumina

Journal Article · Sun Feb 01 04:00:00 EST 1987 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(87)90128-X· OSTI ID:5648324

Hayden, T F; Dumesic, J A

The morphology of monolayer quantities of molybdenum oxide and sulfide phases supported on thin films of nonporous alumina was studied by X-ray photoelectron spectroscopy and conventional and scanning transmission electron microscopy. Following oxidation at 770 K, a strong oxide-support interaction was observed, resulting in a highly dispersed molybdenum phase for loadings below ca. 5 Mo atoms nm/sup -2/. The molybdenum oxide-support interaction was broken by sulfiding in H/sub 2/S/H/sub 2/ at ca. 770 K, with the formation of faceted single crystallites of MoS/sub 2/. The MoS/sub 2/ crystallites were present as hexagonally shaped slabs with one truncated edge and they were bonded with their high-energy edge planes to the alumina surface. The edge planes contacting the gas phase were the (1010) set of planes, while the truncated edge bonded to the surface of alumina was the (2110) plane. After 910 K sulfidation, the particles became larger, and many were oriented with their basal planes parallel to the support. Reoxidation at 770 K dispersed the crystallites due to spreading of molybdenum oxide over alumina. These results can be explained by the formation of Mo-O-Al linkages during oxidation and the breaking of these linkages during sulfiding. As these linkages that anchor the MoS/sub 2/ crystallites to the support are broken, the MoS/sub 2/ basal planes become oriented at angles close to 90/sup 0/ to the support surface. Upon more extensive sulfidation, the MoS/sub 2/ crystallites became oriented with their basal planes parallel to the support when the Mo-O-Al linkages at the edge plane are finally broken.

• Research Organization: Univ. of Wisconsin, Madison
• OSTI ID: 5648324
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 103:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

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