Understanding the Role of Charge Storage Mechanisms in the Electrochromic Switching Kinetics of Metal Oxide Nanocrystals
Understanding the Role of Charge Storage Mechanisms in the Electrochromic Switching Kinetics of Metal Oxide Nanocrystals
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DOI：
10.1021/acs.chemmater.2c00930
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发表时间：
2022-06-08
影响因子：
8.6
通讯作者：
Milliron, Delia J.
中科院分区：
文献类型：
--
作者：
Lu, Hsin-Che;Zydlewski, Benjamin Z.;Milliron, Delia J.
电致变色金属氧化物纳米晶体的发展有望改善传统电致变色智能窗的缓慢开关动力学。然而，在纳米晶体中控制开关动力学的微观过程可能不同于传统的块状材料中的那些，在传统的块状材料中，插层之后的离子扩散通常是速率限制的。在此，通过系统地研究Sn掺杂的In2O3纳米颗粒，正交Nb2O5纳米棒，和单斜Nb12O29纳米片的电致变色响应，我们阐明了不同的电荷存储机制，包括电容充电，表面氧化还原，和嵌入，影响电致变色纳米晶体的开关动力学。纳米晶体在锂和四丁基铵基电解质中在各种电位下还原，以确定哪种电荷存储机制支配其电致变色响应，并且通过基于电容器的充电行为的指数增长模型拟合来量化在还原电位下的光学开关动力学。对于表面占主导地位的电容充电和表面氧化还原机制，观察到的双阶段开关动力学，无论材料，快速切换在还原的早期阶段，并随着时间的推移变得较慢，因为电荷积累在双电层。对于插层机理，观察到由离子插层反应速率控制的单级开关动力学。通过使用光谱电化学方法，我们证明了方法来定义电致变色金属氧化物纳米晶体中的电荷存储机制，并研究了这些机制如何影响电致变色响应的开关动力学。
The development of electrochromic metal oxide nanocrystals holds promise for improving the sluggish switching kinetics of conventional electrochromic smart windows. Nevertheless, the microscopic processes controlling switching kinetics in nanocrystals may differ from those in traditional bulk materials where ion diffusion following intercalation is often rate limiting. Herein, by systematically investigating the electrochromic response of Sn-doped In2O3 nanoparticles, orthorhombic Nb2O5 nanorods, and monoclinic Nb12O29 nanoplatelets, we elucidate how different charge storage mechanisms, including capacitive charging, surface redox, and intercalation, affect the switching kinetics of electrochromic nanocrystals. The nanocrystals were reduced in both lithium- and tetrabutylammonium-based electrolytes at various potentials to determine which charge storage mechanism governs their electrochromic response, and the optical switching kinetics at a reducing potential were quantified by fitting with an exponential-growth model based on the charging behavior of capacitors. For the surface-dominated capacitive charging and surface redox mechanisms, dual-stage switching kinetics were observed regardless of the materials, switching rapidly at the early stage of reduction and becoming slower over time as charge accumulates in the electric double layer. As for the intercalation mechanism, single-stage switching kinetics controlled by the reaction rate of ion intercalation were observed. By using spectroelectrochemical methods, we demonstrated approaches to define the charge storage mechanisms in electrochromic metal oxide nanocrystals and investigated how these mechanisms affect the switching kinetics of the electrochromic response.