Electronic structure and surface kinetics of palladium hydride studied with x-ray photoelectron spectroscopy and electron-energy-loss spectroscopy

X-ray photoelectron spectra and electron-energy-loss spectra (EELS) are presented and interpreted for PdH_~0.8 prepared by in situ loading and cleaning of a 10-{μ}m foil cooled to 80 K. Hydrogenation induces new states with considerable d character 8 eV in the valence band, a slight narrowing of the valence-band spectrum, and a shift of the Fermi level out of the d manifold of states. In the core-line spectra a +0.17-eV binding-energy shift occurs, the asymmetry is reduced, and a shake-up satellite at 6 eV essentially disappears. In the EELS spectra a 7-eV plasmon loss is attenuated and shifted to 5 eV. During degassing experiments, no significant surface depletion is found, and two different rates occur: For concentrations Hₓ0.65 atomic fraction hydrogen ((β phase) an activation energy of 8.1-kcal/mole H₂ is found, while for Hₓ0.65 (two-phase region) the rate is 10⁵ slower, but has a similar activation energy of 9.0-kcal/mole H₂. During this time the surface contains both β and α phases.