Influence of Hydrogen-Incorporation on the Bulk Electronic Structure and Chemical Bonding in Palladium
Lars J. Bannenberg (TU Delft - RID/TS/Instrumenten groep)
Fernando García-Martínez (Deutsches Elektronen-Synchrotron DESY)
Patrick Lömker (Stockholm University)
Robin Y. Engel (Stockholm University)
Christoph Schlueter (Deutsches Elektronen-Synchrotron DESY)
Herman Schreuders (TU Delft - Applied Sciences)
Amy Navarathna (TU Delft - RID/TS/Technici Pool)
Laura E. Ratcliff (University of Tromsø, University of Bristol)
Anna Regoutz (University of Oxford, University College London)
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Abstract
Palladium hydride is a model system for studying metal-hydrogen interactions. Yet, its bulk electronic structure has proven difficult to directly probe, with most studies to date limited to surface-sensitive photoelectron spectroscopy approaches. This work reports the first in situ ambient-pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) study of hydrogen incorporation in Pd thin films, providing direct access to bulk chemical and electronic information at elevated hydrogen pressures. Structural characterization by in situ X-ray diffraction and neutron reflectometry under comparable conditions establishes a direct correlation between hydrogen loading, lattice expansion, and electronic modifications. Comparison with density functional theory (DFT) reveals how hydrogen stoichiometry and site occupancy govern the density of occupied states near the Fermi level. These results resolve long-standing questions regarding PdH and establish AP-HAXPES as a powerful tool for probing the bulk electronic structure of metal hydrides under realistic conditions.
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