现场表面增强红外光谱法研究离子液体体系中可逆锌电极过程的界面结构

发布时间：2018-05-08 07:16

本文选题：离子液体 + 锌　；参考：《上海大学》2015年硕士论文

【摘要】：锌-空气二次电池因其较高的能量密度,丰富易得的电极原材料,受到人们广泛的关注。作为锌-空气二次电池的阳极,锌的可逆电极过程就显得尤其重要。但是在传统的碱性电解液中,锌的沉积总是伴随有枝晶的形成,水溶液的蒸发,氢脆现象的发生等问题。室温离子液体,完全由阴阳离子组成,具有较低的蒸汽压、较好的热稳定性、较宽的电化学窗口等优点,将离子液体作为锌沉积的电解液,有望解决以上碱溶液中所出现的问题。研究表明在不同的离子液体-锌盐混合体系中加入水,会对锌氧化还原反应的电化学性质产生巨大影响。众所周知,锌电极反应发生在电极/离子液体的界面上,该过程与界面上离子的排布密切相关。然而,目前为止,相关的界面结构尚不清楚。因此,研究离子液体混合体系中锌沉积过程中的电极界面结构具有重要意义,同时也可以从界面的角度为电沉积锌提供理论依据。本文将利用现场表面增强红外光谱法并结合电化学测试手段研究几种常见的离子液体及离子液体-水混合体系中锌电沉积过程中的双电层界面结构。首先,研究了BF4-阴离子型离子液体([EMIM]BF4],[BMIM][BF4],[OMIM][BF4])及离子液体-水混合体系中锌的电沉积行为。结果表明随着阳离子尺寸增加,离子液体粘度变大,锌沉积的电位变负,沉积电流密度减小;对于同一离子液体而言,加水后锌沉积电位变得更正,沉积电流密度更大,锌氧化还原可逆性更好。此外,采用表面增强红外吸收光谱分别研究了[BMIM][BF4]+0.4 M Zn(BF4)2和[BMIM][BF4]+0.4 M Zn(BF4)2+5V/V%H2O,两类离子液体体系中可逆锌电极过程的界面结构。结果表明,加水后,水合锌离子吸附在电极上,阴阳离子发生脱附,相应的电极界面模型图被提出。其次,研究了[OTf]-阴离子型离子液体([EMIM][OTf][BMIM][OTf],[OMIM][OTf])及离子液体-水混合体系中锌在金圆盘电极上的电沉积行为。结果显示,加水后,锌在[EMIM][OTf]和[BMIM][OTf]离子液体体系中沉积的电流密度增加,可逆性变好;在[OMIM][OTf]离子液体-水混合体系中,可能电极界面离子液体溶剂层的形成有关,导致锌电流密度变小,锌沉积氧化峰消失。同时,也研究了[BMIM][OTf]+0.4 M Zn(OTf)2和[BMIM][OTf]+0.4 M Zn(OTf)2+5V/V%H2O;[EMIM][OTf]+0.4 M Zn(OTf)2和[EMIM][OTf]+0.4 M Zn(OTf)2+5V/V%H2O四种离子液体体系中锌沉积的电极界面结构。在[OTf]-阴离子型离子液体体系中,由于[OTf]-阴离子会在金电极表面发生特性吸附,所以加水后,电极表面并没有被完全水化。随着电位变负,锌开始沉积,水分子和水合锌离子逐渐吸附到电极上,阴阳离子被取代而发生脱附,并提出了相应的结构模型。最后,研究了两种功能化离子液体([Cp MIM][BF4]和[HOEt MIM][BF4])及离子液体-水混合体系中锌的电沉积行为。结果表明腈基(-CN)和羟基(-OH)的引入更有益于锌沉积。本文创新之处在于利用现场表面增强红外光谱法系统地研究了几种离子液体体系中可逆锌电极过程的界面结构,深入认识了水在锌沉积过程中所起的作用,为离子液体中锌的沉积提供了重要的理论依据。
[Abstract]:Zinc air two battery has attracted wide attention because of its high energy density and abundant available electrode materials. As the anode of zinc air two battery, the reversible electrode process of zinc is especially important. But in the traditional alkaline electrolyte, the deposition of zinc is always accompanied by the formation of dendrites, the evaporation of aqueous solution, and hydrogen embrittlement. Room temperature ionic liquid, which is composed entirely of yin and yang ions, has the advantages of lower steam pressure, better thermal stability and wider electrochemical window. The ionic liquid is used as the electrolyte of zinc deposition. It is expected to solve the problems in the above alkali solution. The study shows that the different ionic liquid zinc salt mixture is found. It is well known that the reaction of zinc electrode occurs at the interface of the electrode / ionic liquid, which is closely related to the arrangement of ions on the interface. However, so far, the related interface structure is not clear. Therefore, the study of zinc precipitation in the ionic liquid mixture system has been studied. The electrode interface structure in the product process is of great significance, and it can also provide a theoretical basis for electrodeposition of zinc from the angle of the interface. In this paper, the double layer of zinc electrodeposition in several common ionic liquids and ionic liquid mixtures is studied by the field surface enhanced infrared spectroscopy and electrochemical measurement. First, the electrodeposition behavior of zinc in the BF4- anionic liquid ([EMIM]BF4], [BMIM][BF4], [OMIM][BF4]) and ionic liquid water mixtures is studied. The results show that the viscosity of the ionic liquid becomes larger, the potential of the zinc deposition is negative, the deposition current density decreases with the increase of the cation size, and the addition of the current density to the same ionic liquid is added. After water, the zinc deposition potential becomes more positive, the deposition current density is greater, and the redox reversibility of zinc is better. In addition, the interface structure of the reversible zinc electrode process in [BMIM][BF4]+0.4 M Zn (BF4) 2 and [BMIM][BF4]+0.4 M Zn (BF4) 2+5V/V%H2O and the two kind of ionic liquid system is studied by surface enhanced infrared absorption spectroscopy. The zinc ion adsorbed on the electrode, the anion and Yang ion degenerated, the corresponding electrode interface model was proposed. Secondly, the electrodeposition behavior of zinc on the gold disk electrode in the [OTf]- anionic ionic liquid ([EMIM][OTf][BMIM][OTf], [OMIM][OTf]) and the ionic liquid water mixing system was studied. The results showed that after adding water, zinc was in [EMIM][OTf] The current density in the [BMIM][OTf] ionic liquid system increases and the reversibility becomes better. In the [OMIM][OTf] ionic liquid water mixture system, the formation of the ionic liquid solvent layer at the electrode interface is related, which leads to the small zinc current density and the zinc deposition oxidation peak disappearing. Meanwhile, the [BMIM][OTf]+0.4 M Zn (OTf) 2 and [BMIM][OTf]+0.4 M are also studied. Zn (OTf) 2+5V/V%H2O, [EMIM][OTf]+0.4 M Zn (OTf) 2 and [EMIM][OTf]+0.4 M Zn (OTf) 2+5V/V%H2O four ionic liquid systems have the electrode interface structure. In the anion ionic liquid system, the anion will be adsorbed on the surface of the gold electrode, so the surface of the electrode is not completely hydrated after water. As the potential changes, zinc begins to deposit, water molecules and zinc ions are gradually adsorbed on the electrode. The anion and Yang ion is replaced, and the corresponding structural model is put forward. Finally, the electrodeposition behavior of two kinds of functional ionic liquids ([Cp MIM][BF4] and [HOEt MIM][BF4]) and the mixed liquid water mixture system are studied. The introduction of nitrile (-CN) and hydroxyl (-OH) is more beneficial to zinc deposition. The innovation of this paper is to systematically study the interface structure of the reversible zinc electrode process in several ionic liquid systems by using the field surface enhanced infrared spectroscopy, and deeply understand the role of water in the zinc deposition process, providing the deposition of zinc in ionic liquids. An important theoretical basis.

【学位授予单位】：上海大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O646.54;TM911.41

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