Impedance Spectroscopic Study Using Nanoporous Electrode on Room Temperature Ionic Liquid-propanol Mixtures

Abstract

AC impedance spectroscopic approach is applied into room temperature ionic liquid (RTIL) based mixtures. The RTIL is hydrophobic 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C₂mim][TFSI]. For higher efficient electric double layer capacitor (EDLC) as an energy storage device, Cu3Au nanoporous electrode is assembled in the [C₂mim][TFSI]-propanol mixtures. Due to high cost and high viscosity of the pure [C₂mim][TFSI], an additive is required in order to achieve the low cost and quick electrochemical response for rapid charge/discharge. Propanol having relative low vapor pressure among alcohols is adequate to reduce viscosity of the hydrophobic RTILs. With nanoporous metallic electrode, the EDL capacitance in the mixtures exceed that in the pure [C₂mim][TFSI]. Also, the capacitance in the mixtures was large enough up to 80 mol% propanol. In addition, isomer effect of propanol was seen in the AC impedance spectra.