How do we learn about chemisorption and physisorption of hydrides and the kinetics of hydrogen adsorption and
desorption? These are profound challenges with us for decades. Soft-x-ray spectroscopy will be will be a unique tool to
study the electronic properties of fundamental materials, nanoporous, and complex hydrides and in-situ study the
kinetics of hydrogen adsorption and desorption. To facilitate the search for most efficient hydrogen-generation and -
storage compounds, a fundamental understanding of the electronic properties is essential. Hydrogen strongly affects the
electronic and structural properties of many materials.
The electronic structure ultimately determines the properties of matter. Photon-in/photon-out soft-x-ray spectroscopy has
been the subject to a revived interest owing to the new generation synchrotron facilities and high performance beamline
and instruments. Soft-x-ray absorption spectroscopy (XAS) probes the local unoccupied electronic structure, soft-x-ray
emission spectroscopy (XES) probes the local occupied electronic structure, and resonant inelastic soft-x-ray scattering
(RIXS) probes the intrinsic low-energy excitations, such as charge transfer, proton energy transfer etc. A number of
examples, including some recent experimental findings, then illustrate the potential of XAS and XES applications in
hydrogen energy sciences.
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