Promoted Hydride/Oxide Exchange in SrTiO by Introduction of Anion Vacancy via Aliovalent Cation Substitution.

We investigated topochemical anion exchange reactions for a Sc-substituted SrTiO perovskite, Sr(TiSc)O□ (y ≤ 0.1), using CaH. It was found that the initial introduction of a small amount of anion vacancies (y/2) is crucial to enhance the anion (H/O) exchangeability. For example, hydride reduction of Sr(TiSc)O yielded the oxyhydride SrTiScOH in which the hydride concentration is increased by 33% with respect to pristine SrTiO (leading to SrTiOH). This observation highlights the importance of anion vacancies to improve anion (H/O) diffusion, which is a well-known strategy for improving oxide anion conductivity, and suggests that such a vacancy-assisted reaction could be applied to other anion exchange reactions (e.g., F/O and N/O) to extend the solubility range.