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.

Topochemical reductions with hydrides: Solid state or gas phase reaction?Figure optionsDownload as PowerPoint slide