Sum Frequency Generation Spectroscopy and Double-Layer Capacitance Studies of the 1-Butyl-3-Methylimidazolium Dicyanamide−Platinum Interface

The orientation of the cation and the anion of 1-butyl-3-methylimidazolium dicyanamide at the platinum-liquid interface, using sum frequency generation (SFG) spectroscopy is reported. Sum frequency spectra at two different polarizations and different potentials are recorded, and analysis of polarization-dependent spectra is performed to estimate the orientation of the dicyanamide anion and the alkyl and ring moieties in the cation as a function of the potential applied to the platinum electrode. In addition, cyclic voltammetry and electrochemical impedance spectroscopy are conducted. A model of the double-layer structure at the electrified interface is presented from the analysis of capacitance and SFG data.