Unraveling the "Seesaw" Competition between the Electrically Driven Reduction and Reoxidation Processes in Ceria with In Situ Electron Microscopy
Unraveling the "Seesaw" Competition between the Electrically Driven Reduction and Reoxidation Processes in Ceria with In Situ Electron Microscopy
复制标题
利用原位电子显微镜揭示二氧化铈中电驱动还原和再氧化过程之间的“跷跷板”竞争
DOI：
10.1002/cctc.201600974
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发表时间：
2016
期刊：
影响因子：
4.5
通讯作者：
Bai Xuedong
中科院分区：
文献类型：
--
作者：
Li Xiaomin;Qi Kuo;Sun Muhua;Huang Qianming;Wei Jiake;Xu Zhi;Wang Wenlong;Bai Xuedong
二氧化铈（CeO 2）的氧化还原行为的改善机制的理解是控制其催化和离子特性，这是在各种技术上重要的应用所涉及的核心。在这里，通过原位电子显微镜的真实的时间时间分辨率，我们提出了强有力的证据，以帮助阐明复杂的相互作用和动力学的电驱动氧化还原平衡在二氧化铈。 在外加电场作用下，观察到夹在Nb掺杂SrTiO 3衬底（阴极）和钨探针（阳极）之间的CeO 2薄膜动态地表现出由于氧空位的有序化和迁移而在立方氧化铈晶格中形成的调制波的跷跷板状可逆向前/向后传播。这种有趣的跷跷板状行为表明，氧化铈的电驱动还原（形成氧空位）与腔室中残留氧气（10 - 6Pa）的动态再氧化（修复氧空位）之间存在微妙的竞争。这一结果提供了重要的新见解，可用于理解氧化铈的氧化还原化学，在以前的研究中，还原和氧化过程被认为是两个看似独立的事件，只有在切换外部热力学条件后才能发生。
An improved mechanistic understanding of the redox behavior of ceria (CeO2) is central to controlling its catalytic and ionic properties, which are involved in a variety of technologically important applications. Here, as enabled by the real‐time temporal resolution of in situ electron microscopy, we present strong evidence to help elucidate the complex interplay and dynamics of the electrically driven redox equilibria in ceria. Under an external electric field, a CeO2film sandwiched between a Nb‐doped SrTiO3substrate (cathode) and a tungsten probing tip (anode) was observed to dynamically exhibit a seesaw‐like, reversible forward/backward propagation of the modulation wave formed in the cubic ceria lattice as a consequence of ordering and migration of oxygen vacancies. Such an interesting seesaw‐like behavior indicates subtle competition between the electrically driven reduction (forming oxygen vacancies) of ceria and its dynamic reoxidation (repairing oxygen vacancies) by residual oxygen gas in the chamber (≈10−6Pa). This result provides important new insight that can be used to understand the redox chemistry of ceria, for which, in previous studies, the reduction and oxidation processes were assumed to be two seemingly separate events that could occur only after switching the external thermodynamic conditions.