Photoelectron spectroscopy study on C 1s peaks before and after Ar+ sputtering on the surface of ionic liquid BmImPF6

This study investigates the effects of Ar+ sputtering on an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF6) with use of X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR). Ar+ sputtering effectively removed surface impurities, enhancing the detection of intrinsic elemental signals. NMR analysis confirmed that the chemical structure of the ionic liquid remained unchanged after sputtering. Differently from solid samples, impurities in liquid samples can migrate within the sample, making the acquisition of a clean surface more challenging and requiring careful attention. These findings demonstrate that Ar+ sputtering is a reliable method to prepare ionic liquid surfaces for XPS analysis, enabling accurate assessment of their true surface state without altering the molecular structure. This study contributes to the methodology for surface characterization of ionic liquids under vacuum conditions, with implications for research in materials science and electrochemistry.