BaScHO: 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 BaScHO was successfully synthesized using a high-pressure technique. Powder X-ray and neutron diffraction experiments investigated the fact that BaScHO adopts a KNiF-type structure with H ions preferentially occupying the apical sites, as supported by theoretical calculations. Electrochemical impedance spectra showed that BaScHO exhibited H conduction and a conductivity of 5.2 × 10 S cm at 300 °C. This value is much higher than that of BaScOH, 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.