Multiphase Nanostructure of a Quinary Metal Oxide Electrocatalyst Reveals a New Direction for OER Electrocatalyst Design
Multiphase Nanostructure of a Quinary Metal Oxide Electrocatalyst Reveals a New Direction for OER Electrocatalyst Design
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DOI：
10.1002/aenm.201402307
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发表时间：
2015-05-20
影响因子：
27.8
通讯作者：
Gregoire, John M.
中科院分区：
文献类型：
--
作者：
Haber, Joel A.;Anzenburg, Eitan;Gregoire, John M.
富含Ce的混合金属氧化物构成了最近发现的一类用于析氧反应（OER）的电催化剂。特别地，在低于10 mA cm（-2）的电流密度下，与相应的过渡金属氧化物相比，Ni0.3Fe0.07Co0.2Ce0.43Ox表现出上级活性，尽管二氧化铈相对不活跃。为了阐明增强的活性和潜在的催化机理，详细的结构表征，这五元氧化物电催化剂的报告。所制备的横截面膜的透射电子显微镜成像和电化学测试后揭示了稳定的两相纳米结构，其由3-5 nm直径的萤石CeO 2微晶与在岩盐NiO结构中合金化的3 -5 nm过渡金属氧化物微晶紧密混合组成。剂量实验表明，大于约1000 e埃（-2）s（-1）的电子通量导致固有的结晶材料变成非晶。采用130 e埃（-2）s（-1）的非常低的剂量率，使用内联全息技术进行原子分辨率成像，以揭示其中过渡金属氧化物纳米晶体与二氧化铈纳米晶体形成原子级尖锐边界的纳米结构，并且这些结果与广泛的同步加速器X射线吸收光谱测量相证实。二氧化铈是一种用于其他非均相和电化学反应的良好研究的助催化剂，并且我们的发现引入了双相助催化作为改进的OER电催化剂的设计概念。
Ce-rich mixed metal oxides comprise a recently discovered class of electrocatalysts for the oxygen evolution reaction (OER). In particular, at current densities below 10 mA cm(-2), Ni0.3Fe0.07Co0.2Ce0.43Ox exhibits superior activity compared to the corresponding transition metal oxides, despite the relative inactivity of ceria. To elucidate the enhanced activity and underlying catalytic mechanism, detailed structural characterization of this quinary oxide electrocatalyst is reported. Transmission electron microscopy imaging of cross-section films as-prepared and after electrochemical testing reveals a stable two-phase nanostructure composed of 3-5 nm diameter crystallites of fluorite CeO2 intimately mixed with 3-5 nm crystallites of transition metal oxides alloyed in the rock salt NiO structure. Dosing experiments demonstrate that an electron flux greater than approximate to 1000 e angstrom(-2) s(-1) causes the inherently crystalline material to become amorphous. A very low dose rate of 130 e angstrom(-2) s(-1) is employed for atomic resolution imaging using inline holography techniques to reveal a nanostructure in which the transition metal oxide nanocrystals form atomically sharp boundaries with the ceria nanocrystals, and these results are corroborated with extensive synchrotron X-ray absorption spectroscopy measurements. Ceria is a well-studied cocatalyst for other heterogeneous and electrochemical reactions, and our discovery introduces biphasic cocatalysis as a design concept for improved OER electrocatalysts.