Hydrogen: Unraveling the Dynamic Nanoscale Reducibility (Ce⁴⁺ → Ce³⁺) of CeO_x–Ru in Hydrogen Activation (Adv. Mater. Interfaces 18/2015)

When exposed to a reactive H2 environment, a cerium oxide model catalyst is shown to undergo complex structural transformations, resulting in a heterogeneous composition. J. I. Flege and co-workers illustrate this process in article number 1500314 with electron microscopy images showing triangular ceria particles at different stages of reduction by hydrogen, leading to the production of water. In situ and real-time micro-spectroscopy and diffraction reveal the nanoscale coexistence of crystallographically-ordered ceria phases, with profound implications on the nature of the reduction and the mechanism for H2 scission.