The interface between Au(100) and 1-butyl-3-methyl-imidazolium-hexafluorophosphate

Abstract

The electrochemical interface of Au(100) and 1-butyl-3-methyl-imidazolium hexafluorophosphate has been characterized by cyclic voltammetry, electrochemical impedance spectroscopy and in situ STM, especially in two distinct potential ranges. In the vicinity of the potential of zero total charge--the value of which has been determined by immersion experiments--charging of the double layer is rather slow, it appears as if the ions comprising the ionic liquid would slowly exchange each other at the surface. In the other, very negative region the ordering of the cations has been observed by STM.

The interface between HOPG and 1-butyl-3-methyl-imidazolium hexafluorophosphate

“…The charging current measured on HOPG | BMIPF6 is lower by a factor of 3 to 5 compared to that measured on Au(100) | BMIPF6, 16 and the same applies for the dc capacitance -defined as the average charging current divided by the scan rate -, that has an approximate value of 7 μF/cm 2 .…”

“…11,12,13 From the fundamental research point of view, the key point of studying metal | IL interfaces is the use of electrodes with well-defined surface structures in combination with high-purity ILs. In accordance with this statement, the interface of gold single crystals with a well-defined surface orientation was recently studied in 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIPF6); 14,15,16 in a home-made guanidinium-based IL; 17 and in 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (BMITf2N). 18 In these studies the Faradaic reaction-free potential regions of the metal | IL electrodes were identified and characterized by cyclic voltammetry (CV), while electrochemical impedance spectroscopy (EIS) was employed in order to determine the interfacial capacitance.…”

“…5 of Ref. 16. Open symbols represent the measured spectrum points, to which the solid lines were fitted using the equivalent circuits of the insets.…”

“…15,16 The focus is on the following questions: i.) What is the physical background of the double-arc on the capacitance spectrum?…”

“…This curve exhibits the same increase of Chf with potential, as obtained from the impedance spectra. As in the case of Au(100) | BMIPF6, 16 we attempted to identify the origin of the equivalent circuit elements. Therefore, we measured impedance spectra at different temperatures (between room temperature and 120 °C).…”