Anion Effects on the Interfacial Structure and Bulk Physical Properties in Choline-Based Hydrogen-Bonded Electrolytes
Anion Effects on the Interfacial Structure and Bulk Physical Properties in Choline-Based Hydrogen-Bonded Electrolytes
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DOI：
10.1021/acs.jpcc.2c01901
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发表时间：
2022-08
期刊：
影响因子：
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通讯作者：
William Dean;Drace Penley;Yun-Yang Lee;Raziyeh Ghahremani;Saudagar Dongare;B. Gurkan
中科院分区：
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作者：
William Dean;Drace Penley;Yun-Yang Lee;Raziyeh Ghahremani;Saudagar Dongare;B. Gurkan
研究了由胆碱 (Ch) 盐与乙酸 (Ac) 和草酸 (Ox) 阴离子组成的电解质与乙二醇 (EG) 的混合物，与含氯 (Cl) 和双（三氟磺酰基）亚胺 (TFSI) 的体系进行比较，以了解阴离子大小和电荷密度对本体电解质和界面性质的影响。这些代表氢键浓电解质，其中 Ch 盐是氢键受体 (HBA)，EG 是氢键供体 (HBD)，HBA:HBD 比例为 1:2 和 1:4。与 ChAc 相比，Ch2Ox 与 EG 中氢键的增加使液体变得更紧密，这与根据密度泛函理论 (DFT) 计算出的 Ox-2 中 HBA:HBD 簇解离能的增加一致，从而导致液体更致密、更粘稠。电化学阻抗谱（EIS）和表面增强拉曼光谱（SERS）用于研究界面电荷密度和电极表面物种。微分电容曲线表明，除 ChAc:EG 外，对电势的依赖性很弱，其中 Ac– 被发现吸附在 Au 表面上，特别是在 +0.055 V vs Ag 准参比条件下，而在玻碳 (GC) 上没有观察到特异性吸附。原位 SERS 测量证实了 ChAc:EG 系统中由于 Au-乙酸盐相互作用而形成了表面层。尽管结构相似，但由于通过氢键强溶剂化 EG 分子，Ox-2 并未表现出特异性结合或电容对电位的任何依赖性。这项研究表明，HBA 的电荷密度会影响浓氢键电解质的体积特性和双电层形成，这与电沉积过程和储能应用中的电化学动力学和形态相关。
Electrolytes consisting of choline (Ch) salts with acetate (Ac) and oxalate (Ox) anions were studied in mixtures with ethylene glycol (EG), in comparison to chloride (Cl)- and bis(trifluorosulfonyl)imide (TFSI)-containing systems to understand the impact of anion size and charge density on the bulk electrolyte and interfacial properties. These represent hydrogen-bonded concentrated electrolytes where the Ch salts are the H-bond acceptors (HBAs) and EG is the H-bond donor (HBD) in 1:2 and 1:4 HBA:HBD ratios. Increased H-bonding in Ch2Ox with EG compacts the liquid compared to ChAc, consistent with the increased dissociation energies of the HBA:HBD clusters with Ox–2calculated by density functional theory (DFT), thus leading to denser and more viscous liquids. Electrochemical impedance spectroscopy (EIS) and surface-enhanced Raman spectroscopy (SERS) were used to investigate interfacial charge density and the electrode surface species. Differential capacitance curves demonstrate weak dependence on potential except for ChAc:EG, where Ac–is found to adsorb on the Au surface, in particular at +0.055 V vs Ag quasi-reference while no specific adsorption was observed on glassy carbon (GC). In situ SERS measurement confirms the formation of a surface layer in the ChAc:EG systems resulting from a Au–acetate interaction. Despite the structural similarities, Ox–2did not show specific binding or any dependence of capacitance on potential as a result of strongly solvating EG molecules via H-bonds. This study shows that the charge density of the HBAs impacts both bulk properties and the electrical double-layer formation in concentrated H-bonded electrolytes that is relevant to electrochemical kinetics and morphology in electrodeposition processes and energy storage applications.