CFN Colloquium

Small clusters exhibit electronic and chemical properties that can differ significantly from that of the bulk and offer a unique opportunity for preparing novel catalysts whose reactivity can be modified at the atomic level. Here, we use mass-selected cluster deposition to prepare model "inverse" catalysts comprised of small metal oxide (MxOy: M = Ti, Nb, Mo, Ce, W) and sulfide (MxSy: M = Mo, W) clusters deposited on Cu and Au surfaces, respectively, for reactivity studies related to the water-gas-shift reaction (WGSR) and CO/CO2 activation. A key advantage of cluster deposition is that it allows control over cluster stoichiometry which provides a means of introducing oxygen/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 of structure and reactions using DFT electronic structure theory. Results will be presented for studies of water dissociation on oxide clusters deposited on Cu surfaces and CO2 binding on K-modified sulfide clusters, as well as very recent measurements using ambient pressure XPS (CSX-2 at NSLS-2) to explore the activity of (TiO2)n/Cu(111) surfaces for the water-gas-shift reaction.