石墨烯
离子液体
电容
电解质
反离子
材料科学
电化学
零电荷点
化学物理
表面电荷
化学工程
离子
分析化学(期刊)
无机化学
化学
电极
纳米技术
物理化学
有机化学
工程类
催化作用
作者
Qianlu Zheng,Zachary A. H. Goodwin,Varun Gopalakrishnan,Alexis Grace Hoane,Ming Han,Ruixian Zhang,Nathaniel Hawthorne,James D. Batteas,Andrew A. Gewirth,Rosa M. Espinosa‐Marzal
出处
期刊:ACS Nano
[American Chemical Society]
日期:2023-05-10
卷期号:17 (10): 9347-9360
被引量:1
标识
DOI:10.1021/acsnano.3c01043
摘要
The performance of electrochemical devices using ionic liquids (ILs) as electrolytes can be impaired by water uptake. This work investigates the influence of water on the behavior of hydrophilic and hydrophobic ILs─with ethylsulfate and tris(perfluoroalkyl)trifluorophosphate or bis(trifluoromethyl sulfonyl)imide (TFSI) anions, respectively─on electrified graphene, a promising electrode material. The results show that water uptake slightly reduces the IL electrochemical stability and significantly influences graphene’s potential of zero charge, which is justified by the extent of anion depletion from the surface. Experiments confirm the dominant contribution of graphene’s quantum capacitance (CQ) to the total interfacial capacitance (Cint) near the PZC, as expected from theory. Combining theory and experiments reveals that the hydrophilic IL efficiently screens surface charge and exhibits the largest double layer capacitance (CIL ∼ 80 μF cm–2), so that CQ governs the charge stored. The hydrophobic ILs are less efficient in charge screening and thus exhibit a smaller capacitance (CIL ∼ 6–9 μF cm–2), which governs Cint already at small potentials. An increase in the total interfacial capacitance is observed at positive voltages for humid TFSI-ILs relative to dry ones, consistent with the presence of a satellite peak. Short-range surface forces reveal the change of the interfacial layering with potential and water uptake owing to reorientation of counterions, counterion binding, co-ion repulsion, and water enrichment. These results are consistent with the charge being mainly stored in a ∼2 nm-thick double layer, which implies that ILs behave as highly concentrated electrolytes. This knowledge will advance the design of IL-graphene-based electrochemical devices.
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