Synthesis, crystal structure, and ionic conductivity of hydride ion-conducting Ln2LiHO3 (Ln = La, Pr, Nd) oxyhydrides

Abstract

Hydride ion (H⁻)-conducting solids could contribute to the development of novel electrochemical devices using unique H⁻ conduction phenomena. However, understanding the new class of H⁻ conducting oxyhydrides is still undergoing. In this study, new H⁻ conducting Ln₂LiHO₃ (Ln = La, Pr, Nd) oxyhydrides were synthesised using a high-pressure (2 GPa) method. Structural analysis revealed that the anion arrangement in the axial sites of the perovskite unit depends on the Ln ions and strongly affects hydride conductivity. Nd₂LiHO₃, which has a space group Immm, in which ∼5% of the O sites (2d) are occupied instead by H, had the highest conductivity at 280 °C of 2.2 × 10⁻⁵ S cm⁻¹. The possibility of long-distance H⁻ diffusion in Ln₂LiHO₃ was computationally investigated. The results corroborate the experimental findings, which indicate that lower O content promotes anion migration.