Yu-Ling Lai

The decomposition of methanol on Au–Pt bimetallic clusters supported by a thin film of Al2O3/NiAl(100)

With various techniques to probe a surface, we studied the decomposition of methanol on Au–Pt bimetallic clusters, of diameter ≤6.0 nm, formed by sequential deposition of Au and Pt evaporated onto thin-film Al2O3/NiAl(100). The surface of the bimetallic clusters comprised both Au and Pt, but the decomposition, through dehydrogenation to CO and scission of the C–O bond, proceeded primarily on the surface Pt. Alloying of Pt with Au altered little the dehydrogenation on the Pt sites. The CO and hydrogen produced from dehydrogenated methanol increased with the extent of Pt sites; the production per surface Pt was comparable to that of Pt clusters. The temperature of the onset of dehydrogenation resembled that of Pt clusters. Little methanol decomposed to CO on the Au sites. Varying the surface structure and composition of the bimetallic clusters affected these properties insignificantly. In contrast to the dehydrogenation, scission of the C–O bond in methanol did not depend exclusively on the concentration of Pt atoms at the surface, given that production of methane from this second channel did not increase with the extent of Pt surface sites. The modified electronic structure of the alloyed Pt controlled the probability of the C–O bond scission. The bimetallic clusters restructured during the reaction such that the Au atoms in the clusters aggregated and decorated the Pt surface, leading to fewer surface Pt and increased mean coordination of surface Au.

Microscopic evidence for the dissociation of water molecules on cleaved GaN(1(1)over bar00)

The dissociation of water molecules absorbed on a cleaved non-polar GaN(11[combining macron]00) surface was studied primarily with synchrotron-based photoemission spectra and density-functional-theory calculations. The adsorbed water molecules are spontaneously dissociated into hydrogen atoms and hydroxyl groups at either 300 or 130 K, which implies a negligible activation energy (<11 meV) for the dissociation. The produced H and OH were bound to the surface nitrogen and gallium on GaN(11[combining macron]00) respectively. These results highlight the promising applications of the non-polar GaN(11[combining macron]00) surface in water dissociation and hydrogen generation.