In Situ Atomic-Scale Probing of the Reduction Dynamics of 2-Dimensional Fe2O3 Nanostructures

摘要

Atomic-scale structural dynamics and phase transformation pathways were probed, in situ, during the hydrogen-induced reduction of Fe2O3 nanostructure bi-crystals using an environmental transmission electron microscope. Reduction commenced with the α-Fe2O3 → γ-Fe2O3 phase transformation of one part of the bi-crystal, resulting in the formation of a two-phase structure of α-Fe2O3 and γ-Fe2O3. The progression of the phase transformation into the other half of the bi-crystalline Fe2O3 across the bi-crystalline boundary led to the formation of a single crystal phase of γ-Fe2O3 with concomitant oxygen-vacancy ordering on every third {422} plane, followed by transformation into Fe3O4. Further reduction resulted in the coexistence of Fe₃O₄, FeO, and Fe via the transformation pathway Fe₃O₄ → FeO → Fe. The series of phase transformations was accompanied with the formation of a Swiss-cheese-like structure, induced by the significant volume shrinkage occurring upon reduction. These results elucidated the atomistic mechanism of the reduction of Fe oxides and demonstrated formation of hybrid structures of Fe oxides via tuning the phase transformation pathway.