Interaction of a Self-Assembled Ionic Liquid Layer with Graphite(0001): A Combined Experimental and Theoretical Study

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• 作者：Florian Buchner ; Katrin Forster-Tonigold ; Maral Bozorgchenani ; Axel Gross ; R. Jürgen Behm
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：January 21, 2016
• 年：2016
• 卷：7
• 期：2
• 页码：226-233
• 全文大小：531K
• ISSN：1948-7185

文摘

The interaction between (sub)monolayers of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide [BMP]⁺[TFSA]^? and graphite(0001), which serves as a model for the anode|electolyte interface in Li-ion batteries, was investigated under ultrahigh vacuum conditions in a combined experimental and theoretical approach. High-resolution scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and dispersion-corrected density functional theory (DFT-D) calculations were employed. After vapor deposition at 300 K, XPS indicates molecular adsorbates with a 1:1 ratio of cations/anions. Cool down to ～100 K leads to the formation of an ordered (2D) crystalline phase, which coexists with a mobile (2D) liquid. DFT-D calculations reveal that adsorbed [BMP]⁺ and [TFSA]^? species are arranged alternately in a row-like adsorption structure (cation–anion–cation–anion) and that adsorption is dominated by dispersion interactions between adlayer and substrate, on the one hand, and electrostatic interactions between the ions in a row, on the other hand. Simulated STM images of that structure closely resemble the experimental molecular resolved STM images and show that the resolved features mostly stem from the cations.