Interaction of Pd electron states with adsorbed hydrogen

• Published in: Surface science 2013-02, Vol.608, p.165-172
• Main Authors: Solov'ev, S.M., Pettenkofer, C., Pronin, I.I., Potekhina, N.D., Petrov, V.N.
• Format: Article
• Language: English
• Subjects: Clusters; Deposition; Electrochemical impedance spectroscopy; Excitation spectra; Graphite; Hydrogen; Image state; Palladium; Pd clusters; Polyethylenes; Spectra; Synchrotron radiation; UV photoelectron spectroscopy
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2012.10.001

Investigations of electrons excited into image states (IS) of Pd clusters and their interaction with adsorbed hydrogen using photoelectron (PE) spectroscopy with synchrotron radiation is presented. Pd clusters were deposited on pyrolytic graphite surfaces which were used as inert substrates. PE spectra measured for Pd clusters at low photon energies show additional peaks at energies of~4.7 and 5.25eV that corresponds to Pd image states at energies EIS−Evac≈−0.75±0.1eV and EIS−Evac≈−0.2±0.1eV. After hydrogen adsorption on graphite with Pd clusters the H-induced features: positive peaks at energy −2eV, −3.5eV, −7eV and a small negative peak at −4.6eV, were observed in the valence band spectra of Pd below EF. While the peaks at −3.5eV and −2eV are the result of the formation of H-induced states in the SBZ the −7eV peak is due to strong interaction of Pd clusters with hydrogen producing a H―Pd bonding adsorbate state. It is proposed that a charge transfer from IS2 to Pd-H bond dominates over the H− anion neutralization via transfer of excess charge from H− to IS1. ► Pd clusters were formed on highly oriented pyrolytic graphite. ► Photo emission spectra with synchrotron irradiation were used for investigation Pd electron states. ► The influence of hydrogen adsorption on Pd electron structure was studied. ► The interaction of electrons in Pd image state with adsorbed hydrogen was found.