| AVS 65th International Symposium & Exhibition | |
| Surface Science Division | Tuesday Sessions |
| Session SS+HC+MI-TuA |
| Session: | Oxides/Chalcogenides: Structures and Reactions |
| Presenter: | Donna Chen, University of South Carolina |
| Authors: | D.A. Chen, University of South Carolina R.P. Galhenage, University of California at Irvine H. Yan, University of Louisiana Layfette D. Le, University of Central Florida T.B. Rawal, University of Central Florida T.S. Rahman, University of Central Florida |
| Correspondent: | Click to Email |
MoSx clusters have been grown on TiO2(110) in order to provide a model surface for better understanding adsorbate interactions and chemical activity of supported MoSx clusters; MoS2 particles have exhibited excellent catalytic activity for a variety of reactions, particularly for hydrodesulfurization and photocatalysis, and interactions with the support are believed to induce new electronic properties. The MoSx clusters were grown by deposition of Mo on titania in an atmosphere of H2S, followed by annealing to 950 K in H2S. Scanning tunneling microscopy experiments show that clusters with elongated, rectangular shapes and flat tops are formed, and the long axes of the clusters have specific orientations with respect to the [001] direction on TiO2(110). In contrast, deposition of Mo in the absence of H2S results in a high density of smaller, round clusters that cover the majority of the surface. The morphologies of MoSx clusters do not change after exposure to various gases (D2, CO, O2, methanol) in ultrahigh vacuum. However, exposure to higher pressures of O2 (250 mTorr) or air causes the clusters to disintegrate as Mo in the clusters becomes oxidized. Temperature programmed desorption studies with CO on the MoSx clusters show a distinct desorption peak at 275 K, which is not observed on metallic Mo or titania. Density functional theory calculations demonstrate that the presence of the titania support changes in the favored adsorption site for CO from the (-1010) edge in the pristine MoS2 to the (10-10) edge for the supported MoS2. Furthermore, the MoSx/TiO2(110) interfacial sites are not favored for CO adsorption.
*This work is partially supported by DOE grant DE-FG02-07ER15842.