The extremely low volatility of ionic liquids (ILs) – salts with melting points typically below 100 °C – enables the use of ultra-high vacuum based surface science methods that were originally developed for solids. X-ray photoelectron spectroscopy (XPS) turned out to be a very powerful tool for IL reaction studies, particularly due the possibility to follow changes in chemical state of the IL via XPS chemical shifts. Moreover, angle-resolved XPS (ARXPS) allows for varying the information depth from about 7-9 nm (0° electron emission angle, more bulk-sensitive) down to 1-1.5 nm (80°, more surface-sensitive); in the latter case, about 80% of the overall XPS intensity arises solely from the outermost IL layer. Thus, differences between the surface layer and the bulk can be accessed in great detail by ARXPS. Within the last years, we demonstrated that a large variety of chemical reactions and reaction mechanisms of different complexity are accessible when using <i>in situ</i> ARXPS to investigate the liquid phase chemistry of ILs. Our studies included CO<sub>2</sub>-capture reactions, acid-base reactions, nucleophilic substitution reactions, a thermochromic transformation of a complex equilibrium, and X-ray induced reactions.

Following reactions in ionic liquids through the outer surface by X-ray photoelectron spectroscopy

255th National Meeting (2018)

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