In Situ Electrochemical Electron Microscopy Study of Oxygen Evolution Activity of Doped Manganite Perovskites
In Situ Electrochemical Electron Microscopy Study of Oxygen Evolution Activity of Doped Manganite Perovskites
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DOI：
10.1002/adfm.201103173
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发表时间：
2012-08-21
影响因子：
19
通讯作者：
Jooss, Christian
中科院分区：
文献类型：
--
作者：
Raabe, Stephanie;Mierwaldt, Daniel;Jooss, Christian
基于锰氧化物化合物的催化剂的基础研究具有很高的兴趣，因为它们提供了研究在从H2O放出O2的过程中活性状态中可变价态的作用的机会。采用原位环境透射电子显微镜（ETEM）结合非原位循环伏安法（ex-situ cyclic voltammetry）研究了Pr掺杂CaMnO 3的掺杂依赖性析氧电催化性能。多相催化的ETEM研究是一个挑战，因为H2O气相中的反应不能直接观察到。结果表明，硅烷被游离氧氧化成固体SiO2-x可用于监测催化析氧。电子能量损失谱（EELS）以及在水蒸气中的近边结构（XANES）的原位X射线吸收研究表明，Mn的价态在活性状态下降低。仔细的TEM分析样品测量的非原位循环伏安法和原位偏压控制的ETEM研究使我们能够区分自形成过程中的氧析出和腐蚀在Pr 1-xCaxMnO 3-H2O界面。包括密度泛函理论（DFT）的计算，在O2的演变活动和缺陷化学在活性状态的趋势可以被校正到掺杂引起的电子能带结构的变化，在A-位掺杂的锰氧化物。
Fundamental studies of catalysts based on manganese oxide compounds are of high interest since they offer the opportunity to study the role of variable valence state in the active state during O2 evolution from H2O. This paper presents a study of doping dependent O2 evolution electrocatalysis of Pr-doped CaMnO3 via in situ environmental transmission electron microscopy (ETEM) combined with ex situ cyclic voltammetry studies. ETEM studies of heterogeneous catalysis are a challenge, since the reactions in the H2O vapor phase cannot directly be observed. It is shown that the oxidation of silane by free oxygen to solid SiO2-x can be used to monitor catalytic oxygen evolution. Electron energy loss spectroscopy (EELS) as well as the in situ X-ray absorption study of near edge structures (XANES) in H2O vapor reveals that the Mn valence is decreased in the active state. Careful TEM analysis of samples measured by ex situ cyclic voltammetry and an in situ bias-controlled ETEM study allows us to distinguish between self-formation during oxygen evolution and corrosion at the Pr1-xCaxMnO3-H2O interface. Including density functional theory (DFT) calculations, trends in O2 evolution activity and defect chemistry in the active state can be correclated to doping induced changes of the electronic band structure in A-site doped manganites.