Abstract: The adsorption behavior of thiocyanate(SCN^-) on the Pt electrode in the room-temperature ionic liquids of 1-n-butyl-3-methylimidazolim tetrafluoroborate([BMIM]BF₄) was investigated by electrochemical in situ surface enhanced Raman spectroscopy(SERS). The results revealed that SCN^- adsorbed onto Pt surface in a wide potential region, and the adsorption behavior of SCN^- changed with the variation of the potential. Different Stark effects were observed in different potential regions, i.e. the S—Pt bonding exhibited the Stark shift of 34 cm^-1/V over the range from -0.9 V to 0.4V, and Stark shift of 40 cm^-1/V over the range from -1.6 V to -1.2 V for the N—Pt interaction. There is a transition region for the S- or N-adsorption between -0.9 V and -1.1 V. The change in the Stark effect in the different potential regions suggests that the potential of zero charge(p_zc) of the [BMIM]BF₄-Pt system is around -1.1 V(vs. Pt).

Key words: Thiocyanate, Room temperature ionic liquid, Surface enhanced Raman spectroscopy(SERS), Pt electrode