Atomic-Scale Insights into the FeO-Mediated Oxide Growth during Iron Oxidation

作者：Mingzi Chen, Yuhui Chen, Jinkai Hu, Zhongkang Han, Wentao Yuan, Ying Jiang, Yong Wang · 发表于：Journal of the American Chemical Society · 年份：2026 · DOI：10.1021/jacs.6c11029 · 研究领域：Iron oxide chemistry and applications、Electrocatalysts for Energy Conversion、Advanced Electron Microscopy Techniques and Applications

Iron (Fe) oxidation represents a prototypical system for understanding gas–solid reactions, directly impacting corrosion science, heterogeneous catalysis, and oxide-heterostructure design. Although the oxide configurations and oxidation pathways have been extensively documented, the atomic-scale structural dynamics that couple gas-surface reactions to solid-state phase transitions remain limited. Here, using in situ atomic-resolution environmental scanning transmission electron microscopy (ESTEM), we prepare atomically flat metal α-Fe(001) surfaces via thermal annealing and reveal a fundamentally different oxidation pathway from Fe to Fe 3 O 4 during cooling under the ESTEM base vacuum. We demonstrate that metastable FeO plays a dynamically sustained role in two intermediate states. First, FeO nucleates on Fe(001) as distinct nanoscale islands below 300 °C, exhibiting a truncated square-pyramidal morphology. Second, FeO is retained as capping layers on the oxide during the transformation of the inner FeO into Fe 3 O 4, creating an inverted phase hierarchy (FeO/Fe 3 O 4 /Fe). The FeO layers provide an active pathway for Fe diffusion, with their growth and transition dominating the subsequent oxide expansion. Despite the distinct growth behaviors of FeO on the (001) and {111} surfaces of oxide, their phase transitions are driven by a common basic unit. Structurally, the FeO-to-Fe 3 O 4 transition is achieved via the translocation of octahedral Fe to tetrahedral sites, accompani...