Abstract
Lithium-beryllium metal hydrides, which are structurally related to their parent compound, BeH2, offer the highest hydrogen storage capacity by weight among the metal hydrides (15.93 wt. % of hydrogen for LiBeH3). Challenging synthesis protocols have precluded conclusive determination of their crystallographic structure to date, but here we analyze directly the hydrogen hopping mechanisms in BeH2 and LiBeH3 using quasielastic neutron scattering, which is especially sensitive to single-particle dynamics of hydrogen. We find that, unlike its parent compound BeH2, lithium-beryllium hydride LiBeH3 exhibits a sharp increase in hydrogen mobility above 265 K, so dramatic that it can be viewed as melting of hydrogen sublattice. We perform comparative analysis of hydrogen jump mechanisms observed in BeH2 and LiBeH3 over a broad temperature range. As microscopic diffusivity of hydrogen is directly related to its macroscopic kinetics, a transition in LiBeH3 so close to ambient temperature may offer a straightforward and effective mechanism to influence hydrogen uptake and release in this very lightweight hydrogen storage compound.
Original language | English |
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Article number | 16244 |
Journal | Scientific Reports |
Volume | 7 |
Issue number | 1 |
DOIs | |
State | Published - Dec 1 2017 |
Funding
Research at the Spallation Neutron Source of Oak Ridge National Laboratory was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. We are grateful to K. Lantzky for help with sample synthesis and to C. Brown, V. Garcia Sakai, G. Gasparovic, R. Paul, and M. Tyagi, who helped with sample characterization and preliminary measurements at the NIST Center for Neutron Research, including observations of a sudden transition in the hydrogen sublattice. JLY acknowledges support from DOD-ARO.