POTENTIAL DEPENDANT ANALYSIS OF 1-BUTYL-3-METHYLIMIDAZOLIUM HEXAFLUOROPHOSPHATE IONIC LIQUID ON PLATINUM ELECTRODE BY SUM FREQUENCY GENERATION SPECTROSCOPY

摘要

Sum Frequency Generation vibrational spectroscopy, SFG, of 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF_6], on a polycrystalline platinum electrode was used to determined the molecular orientation at the liquid-electrode interface under the influence of varied potentials. Cyclic voltammetry was used to identify the electrochemical window of 3V which define the potential range to be analyzed. The peaks intensities were slightly affected as the potential was increased from 0 mV to +1000 mV and more drastically at potentials of -500 mV and +1500 mV. No peaks were observed for a potential of 2000 mV. The changes in the intensity of the peaks for the CH_3(sym) at 2880 cm~(-1), CH_3(asym) and N-CH_3(sym) at 2970 cm~(-1) and H-C(4)C(5)-H(sym) at 3170 cm~(-1) indicate a change of the ionic liquid orientation which is due to the surface charge.