PRX Energy (Jan 2024)

Revealing the Bonding Nature and Electronic Structure of Early-Transition-Metal Dihydrides

  • Curran Kalha,
  • Laura E. Ratcliff,
  • Giorgio Colombi,
  • Christoph Schlueter,
  • Bernard Dam,
  • Andrei Gloskovskii,
  • Tien-Lin Lee,
  • Pardeep K. Thakur,
  • Prajna Bhatt,
  • Yujiang Zhu,
  • Jürg Osterwalder,
  • Francesco Offi,
  • Giancarlo Panaccione,
  • Anna Regoutz

DOI
https://doi.org/10.1103/PRXEnergy.3.013003
Journal volume & issue
Vol. 3, no. 1
p. 013003

Abstract

Read online Read online

Metal hydrides are potential candidates for applications in hydrogen-related technologies, such as energy storage, hydrogen compression, and hydrogen sensing, to name just a few. However, understanding the electronic structure and chemical environment of hydrogen within them remains a key challenge. This work presents a new analytical pathway to explore these aspects in technologically relevant systems using hard x-ray photoelectron spectroscopy (HAXPES) on thin films of two prototypical metal dihydrides: YH_{2−δ} and TiH_{2−δ}. By taking advantage of the tunability of synchrotron radiation, a nondestructive depth profile of the chemical states is obtained using core-level spectra. Combining experimental valence-band (VB) spectra collected at varying photon energies with theoretical insights from density functional theory (DFT) calculations, a description of the bonding nature and the role of d versus sp contributions to states near the Fermi energy are provided. Moreover, a reliable determination of the enthalpy of formation is proposed by using experimental values of the energy position of metal s-band features close to the Fermi energy in the HAXPES VB spectra.