(369h) Hydrogen Adsorption on Metal Hexaboride Surfaces: An Ab Initio Study

Alkaline earth hexaborides are thermoelectric materials with unique thermophysical properties
that have a broad variety of applications with great potential for new uses in fields such as
lightweight armor development, gas storage, and n-type thermoelectrics. Considering their
potential as possible hydrogen storage media, the adsorption properties of these materials have
not yet been extensively studied. In this work, density functional theory (DFT) along with
Car-Parrinello molecular dynamics (CPMD) is used to study the effects of hydrogen loading
and surface terminations on hydrogen adsorption properties within these materials. Idealized
(100) surfaces are determined using the slab method with various surface metal:boron ratios and
geometries, and preferred geometries are found to depend on the particular metal. Hydrogen
effects are studied with CPMD and self-consistent field calculations and show a theoretical
maximum loading on the surface. These results provide very valuable insights on the physical
and chemical mechanisms of hydrogen adsorption in metal hexaboride materials.