Interactions of Ionic Liquid and Surfaces of Graphene Related Nanoparticles under High Pressures
High-pressure infrared spectroscopy was used to study the interactions between 1-methyl-3-propylimidazolium iodide [MPIM]I and graphene-based nanoparticles. The results obtained at ambient pressure indicate the imidazolium ring of the cation seems to be a more favorable moiety for adsorption than alkyl C-H groups at ambient pressure. Upon increasing the pressure, the dominant C2-H band of pure [MPIM][I] yields a significant red frequency shift. As the mixtures, i.e., graphene oxide (GO)/[MPIM][I], reduced graphene oxide (RGO)/[MPIM][I], and graphene (G)/[MPIM][I], were compressed, mild shifts in the C2-H absorption frequency were observed. The absence of drastic red-shifts suggests that the local C2-H structures may be perturbed by the addition of GO, RGO, and G under high pressures. When pure [MPIM][I] was compressed from ambient to 0.4 GPa, the alkyl C-H band at ca. 2964 cm-1 was blue-shifted to 2984 cm-1. This discontinuous jump occurring around 0.4 GPa becomes less obvious for the mixtures GO/[MPIM][I], RGO/[MPIM][I], and G/[MPIM][I]. This study results suggest that the addition of GO, RGO, and G can disturb the local structures of alkyl C-H under high pressures, demonstrating that high pressures may have the potential to tune the strength of ionic liquid-surface interactions and the performance of energy storage devices (e.g. supercapacitor).