Ba2ScHO3: H Conductive Layered Oxyhydride with H Site Selectivity

Hydride (H) conduction is a new frontier related to hydrogen transport in solids. Here, a new H conductive oxyhydride Ba2ScHO3 was successfully synthesized using a high-pressure technique. Powder X-ray and neutron diffraction experiments investigated the fact that Ba2ScHO3 adopts a K2NiF4-type structure with H ions preferentially occupying the apical sites, as supported by theoretical calculations. Electrochemical impedance spectra showed that Ba2ScHO3 exhibited H conduction and a conductivity of 5.2 × 10–6 S cm–1 at 300 °C. This value is much higher than that of BaScO2H, which has an ideal perovskite structure, suggesting the advantage of layered structures for H conduction. Tuning site selectivity of H ions in layered oxyhydrides might be a promising strategy for designing fast H conductors applicable for novel electrochemical devices.