Small clusters consisting of tens of atoms can exhibit electronic and chemical properties distinct from the bulk and offer the possibility of preparing novel nanocatalysts whose properties can be modified at the atomic level. In this work, we use mass-selected cluster deposition to prepare model “inverse” catalysts comprised of small metal oxide (MxOy: M = Ti, Nb, Mo, W) and sulfide (MxSy: M = Mo, W) clusters deposited onto metal surfaces for investigations of interfacial electronic structure and reactivity. A key feature of mass-selected cluster deposition is that it allows control over cluster stoichiometry which provides a means of introducing oxygen or sulfur “vacancies” and varying the average cation oxidation state. Moreover, the use of well-ordered supports and size-selected clusters is ideally suited for computational modeling by DFT electronic structure theory for structure determination, identifying active sites and elucidating reaction mechanisms. Results will be presented for studies of metal oxide clusters deposited on Cu(111) surfaces where we have examined the correlation of interfacial charge transfer with reactivity for water dissociation, as well as the nature of the active sites on the clusters. We also report findings on the use of alkali metals to promote CO2 adsorption and reaction on surfaces of mass-selected Mo and W sulfide clusters deposited on Au(111). Finally, we will present the results of recent studies of the mechanism for the water-gas-shift reaction on metal oxide clusters on Cu(111) surfaces using ambient pressure XPS via the observation of O-vacancy formation and the appearance of reaction intermediates. This work was carried out at Brookhaven National Laboratory under Contract No. DE-SC0012704 with the U.S Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences, and Biosciences within the Office of Basic Energy Sciences.

Electronic structure and reactivity of cluster-based nanocatalysts

255th National Meeting (2018)

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