Zhu Wenhui, Winterstein Jonathan, Maimon Itai, Yin Qiyue, Yuan Lu, Kolmogorov Aleksey N, Sharma Renu, Zhou Guangwen
Department of Mechanical Engineering & Materials Science and Engineering Program, State University of New York, Binghamton, NY 13902, USA.
Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
J Phys Chem C Nanomater Interfaces. 2016 Jul 14;120(27):14854-14862. doi: 10.1021/acs.jpcc.6b02033. Epub 2016 Jun 20.
The atomic-scale reduction mechanism of α-FeO nanowires by H was followed using transmission electron microscopy to reveal the evolution of atomic structures and the associated transformation pathways for different iron oxides. The reduction commences with the generation of oxygen vacancies that order onto every 10 [Formula: see text] plane. This vacancy ordering is followed by an allotropic transformation of α-FeO → γ-FeO along with the formation of FeO nanoparticles on the surface of the γ-FeO nanowire by a topotactic transformation process, which shows 3D correspondence between the structures of the product and its host. These observations demonstrate that the partial reduction of α-FeO nanowires results in the formation of a unique hierarchical structure of hybrid oxides consisting of the parent oxide phase, γ-FeO, as the one-dimensional wire and the FeO in the form of nanoparticles decorated on the parent oxide skeleton. We show that the proposed mechanism is consistent with previously published and our density functional theory results on the thermodynamics of surface termination and oxygen vacancy formation in α-FeO. Compared to previous reports of α-FeO directly transformed to FeO, our work provides a more in-depth understanding with substeps of reduction, i.e., the whole reduction process follows: α-FeO → α-FeO superlattice → γ-FeO + FeO→ FeO.
利用透射电子显微镜跟踪了H对α-FeO纳米线的原子尺度还原机制，以揭示不同铁氧化物的原子结构演变及相关转变途径。还原过程始于氧空位的产生，这些氧空位有序排列在每10个[公式：见正文]平面上。这种空位有序排列之后是α-FeO向γ-FeO的同素异形转变，同时通过拓扑转变过程在γ-FeO纳米线表面形成FeO纳米颗粒，这表明产物与其主体结构之间存在三维对应关系。这些观察结果表明，α-FeO纳米线的部分还原导致形成一种独特的混合氧化物分级结构，该结构由母体氧化物相γ-FeO作为一维线和以纳米颗粒形式装饰在母体氧化物骨架上的FeO组成。我们表明，所提出的机制与先前发表的以及我们关于α-FeO表面终止和氧空位形成热力学的密度泛函理论结果一致。与先前关于α-FeO直接转变为FeO的报道相比，我们的工作对还原的子步骤提供了更深入的理解，即整个还原过程如下：α-FeO→α-FeO超晶格→γ-FeO + FeO→FeO。
