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Visualization of Colloidal Nanocrystal Formation and Electrode–Electrolyte Interfaces in Liquids Using TEM
Accounts of Chemical Research ( IF 18.3 ) Pub Date : 2017-08-07 00:00:00 , DOI: 10.1021/acs.accounts.7b00161
Zhiyuan Zeng 1 , Wenjing Zheng 1, 2 , Haimei Zheng 1, 3
Affiliation  

Transmission electron microscopy (TEM) has become a powerful analytical tool for addressing unique scientific problems in chemical sciences as well as in materials sciences and other disciplines. There has been a lot of recent interest in the development and applications of liquid phase environmental TEM. In this Account, we review the development and applications of liquid cell TEM for the study of dynamic phenomena at liquid–solid interfaces, focusing on two areas: (1) nucleation, growth, and self-assembly of colloidal nanocrystals and (2) electrode–electrolyte interfaces during charge and discharge processes. We highlight the achievements and progress that have been made in these two topical areas of our studies. For example, tracking single platinum particle growth trajectories revealed that two different pathways of growth, either by monomer attachment or coalescence between nanoparticles, led to the same particle size. With the improved spatial resolution and fast electron detection, we were able to trace individual facet development during platinum nanocube platinum nanocube growth. The results showed that different from the surface energy minimization rule prediction, the growth rates of all low-energy facets, such as {100}, {110}, and {111}, were similar. The {100} facets stopped growth early, and the continuous growth of the rest facets resulted in a nanocube. Density functional theory calculations showed that the amine ligands with low mobility on the {100} facets blocked the further growth of the facets. The effect of the ligand on nanoparticle shape evolution were further studied systematically using a Pt–Fe nanoparticle system by changing the oleylamine concentration. With 20%, 30%, or 50% oleylamine, Pt–Fe nanowires or nanoparticles with different morphologies and stabilities were achieved. Real-time imaging of nanoparticles in solution also enabled the study of interactions between nanoparticles during self-assembly. We further compared the study of noble-metal nanoparticles and transition-metal oxides in a liquid cell to elucidate the nanoparticle formation mechanisms. In the second part of this Account, we review the study of electrolyte–electrode interfaces by the development of electrochemical liquid cell TEM. The formation of single-crystalline Pb dendrites from polycrystalline branches and Li dendrite growth in a commercial electrolyte for Li ion batteries were observed. We also studied lithiation reactions of MoS2 and Au electrodes. MoS2 nanoflakes on the Ti electrode underwent irreversible decomposition, resulting in the vanishing of the MoS2 active nanoflakes. More detailed study using nanobeam diffraction indicated that the MoS2 nanoflakes were broken down into small nanoparticles as a result of the fast discharge. For the lithiation of Au electrodes, three distinct types of morphology changes during reactions were revealed, including gradual dissolution, explosive reaction, and local expansion/shrinkage. Additionally, we studied electrolyte decomposition reactions such as bubble formation and solid electrolyte interphase formation. At the end, our perspective on the challenges and opportunities in the applications of liquid phase environmental TEM for the study of liquid chemical reactions is provided.

中文翻译:

使用TEM可视化液体中的胶体纳米晶体形成和电极-电解质界面

透射电子显微镜(TEM)已成为解决化学科学以及材料科学和其他学科中独特的科学问题的强大分析工具。最近,人们对液相环境TEM的开发和应用产生了浓厚的兴趣。在本报告中,我们回顾了液体细胞TEM的研究及其在液-固界面处的动态现象的研究和应用,重点关注两个领域:(1)胶体纳米晶体的成核,生长和自组装;(2)电极–在充电和放电过程中的电解质界面。我们重点介绍了我们在这两个主题研究领域所取得的成就和进步。例如,追踪单个铂粒子的生长轨迹表明,两种不同的生长途径,无论是单体附着还是纳米颗粒之间的聚结,都会导致相同的粒径。通过改进的空间分辨率和快速的电子检测,我们能够追踪铂纳米立方体铂纳米立方体生长过程中各个方面的发展。结果表明,与表面能最小化规则的预测不同,{100},{110}和{111}等所有低能面的增长率相似。{100}构面在早期停止了增长,其余构面的持续增长产生了纳米立方体。密度泛函理论计算表明,{100}面上的低迁移率胺配体阻止了面的进一步生长。通过改变油胺的浓度,使用Pt-Fe纳米粒子系统进一步系统地研究了配体对纳米粒子形状演变的影响。通过使用20%,30%或50%的油胺,可以获得具有不同形态和稳定性的Pt-Fe纳米线或纳米颗粒。溶液中纳米颗粒的实时成像还可以研究自组装过程中纳米颗粒之间的相互作用。我们进一步比较了贵金属纳米颗粒和过渡金属氧化物在液体电池中的研究,以阐明纳米颗粒的形成机理。在本报告的第二部分中,我们回顾了电化学液体电池TEM的发展对电解质-电极界面的研究。观察到在商用锂离子电池电解液中多晶分支形成的单晶Pb树枝状晶体和Li树枝状晶体的生长。我们还研究了MoS的锂化反应2和金电极。Ti电极上的MoS 2纳米薄片发生不可逆的分解,导致MoS 2活性纳米薄片消失。使用纳米束衍射的更详细研究表明,MoS 2由于快速放电,纳米薄片被分解成小的纳米颗粒。对于金电极的锂化,揭示了反应期间三种不同类型的形态变化,包括逐渐溶解,爆炸反应和局部膨胀/收缩。另外,我们研究了电解质分解反应,例如气泡形成和固体电解质界面形成。最后,我们就液相环境TEM在液相化学反应研究中的应用所面临的挑战和机遇提出了自己的观点。
更新日期:2017-08-07
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