X-ray Photoelectron Spectroscopy of 1-Butyl-3-ethylimidazolium Ionic Liquids: The Impact of Ethyl Group on the Electronic Environment of the Cation and the Anion

In this study, X-ray photoelectron spectroscopy is used to analyze two 1-butyl-3-ethylimidazolium ionic liquids. A reliable fitting model is developed for the C 1s region. The structure and surface purity are confirmed. The XP spectra are compared to those of 1-butyl-3-methylimidazolium ionic liquids. The impact of the ethyl group substituted to N3 position on the electronic environment of the cation and the anion is investigated respectively. It is concluded that for the more basic anion, such an impact is focused on the cationic nitrogen atom; whilst for the less basic anion, the influence is found more noticeable on anion-based components.