Determination of Electrode Kinetics Parameters from Dynamic Electrochemical Impedance Spectroscopy Measurements via Potential-Program Invariant Functions.

Dynamic electrochemical impedance spectroscopy, dEIS, comprises repetitive impedance spectrum measurements while slow scan-rate voltammetry is running. Its main virtue is the short measurement time, reducing the danger of contamination of the electrode surface. To further the use of dEIS, we have recently elaborated a set of theories aimed at the related data processing for three groups of fundamental electrode reactions: diffusion-affected charge transfer, charge transfer of surface-bound species, and adsorption-desorption. These theories yielded equations by which the voltammograms can be transformed to potential-program invariant forms, allowing an easy calculation of the rate coefficients; similar equations have been derived for the potential dependence of equivalent circuit parameters obtained from the impedance spectra. In this Perspective, the above derivations are condensed into a single, unified one. The theory is recommended to evaluate electrode kinetic measurements, particularly when the potential dependence of rate coefficients is under study.

The metal-ionic liquid interface as characterized by impedance spectroscopy and in situ scanning tunneling microscopy.

We summarize our results of electrochemical measurements carried out on inert or close-to-inert metals in ionic liquids, with the aim to explore the metal|ionic liquid interface structure. To this we used electrochemical methods: cyclic voltammetry, impedance spectroscopy, potential of zero total charge measurements and structure-sensitive techniques, such as in situ scanning tunneling spectroscopy. The studied systems were mostly single crystals of noble metals in imidazolium-based ionic liquids. The two main findings are: (i) in the potential window where no Faradaic reactions occur, the interfacial capacitance exhibits a frequency dependence due to double-layer rearrangement processes and (ii) in certain cases ordered anion and cation structures exist at the interface.

The interfaces of Au(111) and Au(100) in a hexaalkyl-substituted guanidinium ionic liquid: an electrochemical and in situ STM study.

Five hexaalkylguanidinium-based ionic liquids have been synthesised, and based on their cyclic voltammograms the most suited one, N,N-dibutyl-N',N'-diethyl-N'',N''-dimethylguanidinium bis(trifluoromethylsulfonyl)imide, has been chosen for electrochemical studies. The surface interaction of this room-temperature ionic liquid with single crystalline gold surfaces (Au(100) and Au(111)) has been investigated using cyclic voltammetry, impedance spectroscopy and in situ scanning tunnelling microscopy (STM). The interfacial capacitance was found to be very low; STM measurements revealed the hex-reconstruction and herringbone reconstruction for Au(100) and for Au(111), respectively, at negative potentials; that is, at these potentials no hints for ad-structures of the cation could be found.