Promoted Hydride Substitution in BaTiO₃ Cubes

We report the synthesis of perovskite oxyhydride BaTiO_3-<i>x</i>H<i>_x</i> cubes (100-300 nm) using the topochemical hydride reaction of the hydrothermally synthesized oxide. X-ray and neutron diffraction studies revealed that the anion (hydride/oxide) exchange is greatly improved, leading to a maximum hydride content of 0.7, which is higher than previously reported, while no reaction is seen for those with oleic acid on their surface. These results indicate that the well-defined {100} facets, as well as the absence of organic residues, are crucial for promoting hydrogenation. Kissinger analysis on BaTiO_2.3H_0.7 yielded an activation energy of 165 kJ/mol, much lower than that of BaTiO_2.4H_0.6 (313 kJ/mol). In contrast to oxides, oxyhydrides with well-defined facets have not been reported before; thus, this study opens new avenues for the rational synthesis of oxyhydride materials with controlled chemical composition and morphology.