Local structures and dynamics of interfacial imidazolium-based ionic liquid depending on the electrode potential using electrochemical attenuated total reflectance ultraviolet spectroscopy
Local structures and dynamics of interfacial imidazolium-based ionic liquid depending on the electrode potential using electrochemical attenuated total reflectance ultraviolet spectroscopy
复制标题
使用电化学衰减全反射紫外光谱法研究取决于电极电位的界面咪唑基离子液体的局部结构和动力学
DOI：
10.1016/j.saa.2022.121040
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Fukui Ken-ichi
中科院分区：
文献类型：
--
作者：
Imai Masaya;Tanabe Ichiro;Sato Taiki;Fukui Ken-ichi
近年来，离子液体(ILS)作为性能安全的锂离子电池电解液受到了人们的广泛关注。本文利用衰减全反射远深紫外光(ATR-FUV-DUV)光谱对电化学反应的关键--电化学界面上IL的动力学进行了监测。将ATR-FUV-DUV光谱仪与Kretschmann型(全金属镀膜棱镜)电化学装置相结合，组装了一套独创的测量系统。对1-乙基-3-甲基咪唑双(三氟甲磺酰基)亚胺([EMIM][TFSI])/铂电极(∼7 nm)界面进行了光谱测量和归属。在FUV和DUV区域入射的光进入由[EMIM][TFSI]/铂电极/ATR蓝宝石棱镜组成的测量系统，并在180-450 nm范围内测量了随电位变化的吸收光谱。这种现场光谱技术的独特之处在于可以获得界面IL的电子跃迁光谱。通过切换施加的电位，跟踪了450 nm和221 nm波长下的时间光谱变化(即弛豫信号)，其中IL的直接电子吸收分别是活跃的和不活跃的。比较这些弛豫时间，发现221 nm处的吸收信号变化比450 nm处的慢。这表明影响界面离子液体电子吸收的分子构象变化缓慢。考虑到金属表面分子的表面法偶极子选择规则，我们认为分子构象的缓慢变化可以归因于[EMIM]+的界面取向依赖于电势。
Recently, ionic liquids (ILs) have attracted attention as prospective electrolytes for Li-ion batteries, with safe performance. Herein, the dynamics of the IL at the electrochemical interface, which is the key to the electrochemical reaction, was monitored using attenuated total reflectance far- and deep-ultraviolet (ATR-FUV-DUV) spectroscopy. An original measurement system, which combined an ATR-FUV-DUV spectrometer with a Kretschmann type (fully metal-coated prism) electrochemical setup, was assembled. Spectral measurements and assignments were performed for the 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI])/Pt electrode (∼7 nm) interface. The incident light in the FUV and DUV regions entered a measurement system comprising an [EMIM][TFSI]/Pt electrode/ATR sapphire prism, and the potential-dependent absorption spectra were measured in the 180–450 nm range. Thisin-situspectroscopic technique is unique in that the electronic transition spectra of the interfacial IL can be obtained. By switching the applied potentials, temporal spectral changes (i.e. relaxation signals) were tracked at wavelengths of 450 nm and 221 nm, where the direct electronic absorption of the IL was active and inactive, respectively. Comparing these relaxation times, it was revealed that the absorption signal at 221 nm changed more slowly than that at 450 nm. This indicated that the molecular conformations that affected the electronic absorption of the interfacial ILs changed slowly. Considering the surface-normal dipole selection rule for molecules on a metal surface, it is suggested that the slow changes in the molecular conformations can be ascribed to the potential-dependent interfacial orientations of [EMIM]+.