Room-Temperature Fast H– Conduction in Oxygen-Substituted Lanthanum Hydride

The hydride ion (H–) is a unique anionic species that exhibits high reactivity and chemical energy. H– conductors are key materials to utilize advantages of H– for applications, such as chemical reactors and energy storage systems. However, low H– conductivity at room temperature (RT) in current H– conductors limit their applications. In this study, we report a H– conductivity of ∼1 mS cm–1 at RT, which is higher by 3 orders of magnitude than that of the best conductor, in lightly oxygen-doped lanthanum hydride, LaH3–2xOx with x < 0.25. The oxygen concentration (x) is crucial in achieving fast H– conduction near RT; the low activation barrier of 0.3–0.4 eV is attained for x < 0.25, above which it increases to 1.2–1.3 eV. Molecular dynamics simulations using neural-network potential successfully reproduced the observed activation energy, revealing the presence of mobile and immobile H–.