Electronic Structure of Catalytic Metal Clusters Studied by X-Ray Photoemission Spectroscopy

Pd and Pt clusters on carbon substrates have been studied by x-ray photoemission spectroscopy (XPS). Variations in valence- and core-level spectra with cluster size have been observed. Single-atom centers appear to exist in the $d^9{s}^1$ configuration. The $d$-electron count increases with cluster size, and in the case of Pt a correlation between $d$-orbital occupation and catalytic activity in electroless nickel deposition is observed.