Direct Visualization of Atomic-Scale Heterogeneous Structure Dynamics in MnO2 Nanowires,ACS Applied Materials & Interfaces

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Direct Visualization of Atomic-Scale Heterogeneous Structure Dynamics in MnO2 Nanowires
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-07-08 , DOI: 10.1021/acsami.1c07929
Xin Peng _{1,

2} , Haoyang Peng _{1,

2} , Kangning Zhao ₃ , Yuxi Zhang _{1,

2} , Fanjie Xia _{1,

2} , Jiahui Lyu _{1,

2} , Gustaaf Van Tendeloo _{2,

4} , Congli Sun _{1,

2} , Jinsong Wu _{1,

2}

Affiliation

Manganese oxides are attracting great interest owing to their rich polymorphism and multiple valent states, which give rise to a wide range of applications in catalysis, capacitors, ion batteries, and so forth. Most of their functionalities are connected to transitions among the various polymorphisms and Mn valences. However, their atomic-scale dynamics is still a great challenge. Herein, we discovered a strong heterogeneity in the crystalline structure and defects, as well as in the Mn valence state. The transitions are studied by in situ transmission electron microscopy (TEM), and they involve a complex ordering of [MnO₆] octahedra as the basic building tunnels. MnO₂ nanowires synthesized using solution-based hydrothermal methods usually exhibit a large number of multiple polymorphism impurities with different tunnel sizes. Upon heating, MnO₂ nanowires undergo a series of stoichiometric polymorphism changes, followed by oxygen release toward an oxygen-deficient spinel and rock-salt phase. The impurity polymorphism exhibits an abnormally high stability with interesting small-large-small tunnel size transition, which is attributed to a preferential stabilizer (K⁺) concentration, as well as a strong competition of kinetics and thermodynamics. Our results unveil the complicated intergrowth of polymorphism impurities in MnO₂, which provide insights into the heterogeneous kinetics, thermodynamics, and transport properties of the tunnel-based building blocks.

中文翻译：

MnO ₂纳米线中原子级异质结构动力学的直接可视化

锰氧化物由于其丰富的多态性和多价态而引起了极大的兴趣，这在催化、电容器、离子电池等方面产生了广泛的应用。它们的大部分功能与各种多态性和 Mn 价态之间的转变有关。然而，它们的原子尺度动力学仍然是一个巨大的挑战。在此，我们发现晶体结构和缺陷以及 Mn 价态存在强烈的异质性。通过原位透射电子显微镜 (TEM) 研究转变，它们涉及 [MnO ₆ ] 八面体的复杂排序作为基本构建隧道。的MnO ₂使用基于溶液的水热法合成的纳米线通常表现出大量具有不同隧道尺寸的多晶型杂质。在加热时，MnO ₂纳米线经历一系列化学计量多晶型变化，然后向缺氧尖晶石和岩盐相释放氧。杂质多态性表现出异常高的稳定性和有趣的小-大-小隧道尺寸转变，这归因于优先稳定剂 (K ⁺ ) 浓度以及动力学和热力学的强烈竞争。我们的结果揭示了 MnO ₂中多晶型杂质的复杂共生，它提供了对基于隧道的构建块的异质动力学、热力学和传输特性的见解。

更新日期：2021-07-21

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