Trapping a Ru2O3 Corundum-like Structure at Ultrathin, Disordered RuO2 Nanoskins Expressed in 3D

Abstract

Protocols that express functional materials in a way that amplifies their surface-to-volume ratio offer a means to probe the structural ambiguity and surface-mediated reactivity of technologically important materials. We previously reported that three-dimensional (3D) ultraporous scaffolds, such as silica aerogels, silica fiber paper, and carbon nanofoam paper (CNF), provide a form factor that expresses energy-storing, catalytic ruthenium oxide (RuOx) as essentially all-surface—and a highly disordered one at that. To track the chemical state and solid-state structure of the 3D-expressed RuOx nanoskins as a function of thermal processing, we use X-ray near-edge structure (XANES), extended X-ray fine structure (EXAFS), and differential pair-distribution function (DPDF) analyses. We find that a Ru-centered ∼2.4 A correlation present in the as-deposited oxide, also observed in PDF analysis of RuO2·nH2O but previously unassigned, fits the metastable corundum-like Ru2O3 structure. This corundum-like feature dim...