Probing the adsorption of methylimidazole at ionic liquids/Cu electrode interface by surface‐enhanced Raman scattering spectroscopy

Abstract

Two kinds of room-temperature ionic liquids, 1-butyl-3-methylimidazolium bromide ([BMIM]Br) and 1-butyl-3-methylimidazolium tetrafluoroboride ([BMIM]BF4 ), were used as solvent, and the adsorption of the ionic liquids themselves and of N-methylimidazole (NMIM) were investigated by electrochemical surface-enhanced Raman scattering (SERS) over a wide potential window. The results revealed that the cation of ionic liquid adsorbed onto Cu surface with different configurations in different potential ranges. When the potential was changed from the negative to the positive range, the orientation underwent a change from flat to vertical, and the onset potential for the orientation change was dependent on the types of anion of the ionic liquid. The ionic liquid in bulk solution exhibited a remarkable effect on the adsorption of NMIM. The electrode surface structure changed from adsorbing the ionic liquid at the negative potential to coadsorbing the ionic liquid and NMIM at relative positive potential for the [BMIM]BF 4 liquids, and formed films of NMIM at extremely positive potential. Due to the strong specific adsorption of Br − , the coadsorption of ionic liquid and NMIM was not observed in the system [BMIM]Br. By simulating the electrode surroundings, two surface complexes [Cu(NMIM) 4 Br]Br·H 2 O and [Cu(NMIM) 4 ](BF 4 ) 2 were synthesized by the electrochemical method in the corresponding ionic liquids for modeling the surface coordination chemistry of NMIM. The surface coordination configuration of NMIM and ionic liquids is proposed.

The Electrode/Ionic Liquid Interface: Electric Double Layer and Metal Electrodeposition

“…On the other hand, with a huge enhancement factor (ca. 10 6 ) of surface signals from rough surfaces, SERS has also been applied to studies of ionic liquid systems [80][81][82] with sufficient detection sensitivity in the low-wavenumber region (down to ca. 100 cm À1 ), which is important to provide ion-surface bonding information at the electrode/ionic liquid interfaces.…”

In situ PM-IRRAS of a glassy carbon electrode/deep eutectic solvent interface

“…Mainly because the former has been formulated to explain diluted electrolytes, in which the ions are treated as point charges, whereas RTILs consist of neat ionic fluids. [13][14][15] Several surface sensitive spectroscopic techniques have been used to investigate RTIL/electrode interfaces, including sum frequency generation (SFG), [16][17][18][19] surface-enhanced Raman spectroscopy (SERS), 20,21 surface-enhanced infrared absorption spectroscopy (SEIRAS), 22,23 subtractive normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) 24 and infrared reflection absorption spectroscopy (IRRAS). Multilayers of alternating ions with well ordered compact layers of RTILs have been proposed to explain such interfaces.…”

Extending the shell-isolated nanoparticle-enhanced Raman spectroscopy approach to interfacial ionic liquids at single crystal electrode surfaces

“…Some studies employing fourier transform infrared reflection spectroscopy (FTIRAS), 19 surface enhanced infrared adsorption spectroscopy (SEIRAS), 20 sum frequency generation (SFG) 21,22 and surface enhanced Raman spectroscopy (SERS) [23][24][25][26][27] suggest the orientation change of imidazolium rings from vertical-standing to flat-lying at Pt, Cu and Ag electrode surfaces as the potentials are made more negative.…”