Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports

The interfacial electronic structure of various size-selected metal oxide nanoclusters (M3Ox; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu2O supports were investigated by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surface dipoles are negative for all clusters on Cu(111) and Cu2O/Cu(111), but those on the Cu2O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu2O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer,...