Gas phase contributions to topochemical hydride reduction reactions

•SrFeO2 and LaNiO2 were prepared by topochemical reduction of oxides.•Separating the reducing agent (CaH2, Mg metal) from the oxide still results in reduction.•Such topochemical reactions can occur in the gas phase.

Alkali and alkali earth hydrides have been used as solid state reductants recently to yield many interesting new oxygen-deficient transition metal oxides. These reactions have tacitly been assumed to be a solid phase reaction between the reductant and parent oxide. We have conducted a number of experiments with physical separation between the reductant and oxides, and find that in some cases reduction proceeds even when the reagents are physically separated, implying reactions with in-situ generated H2 and, to a lesser extent, getter mechanisms. Our findings change our understanding of these topochemical reactions, and should enhance the synthesis of additional new oxides and nanostructures.

Graphical abstractTopochemical reductions with hydrides: Solid state or gas phase reaction?Figure optionsDownload full-size imageDownload as PowerPoint slide