Structural Changes of Au(111) Single‐Crystal Electrode Surface in Ionic Liquids

Abstract

Despite a persistent interest in using ionic liquids (ILs) as an electrolyte for various electrochemical applications, the fundamental understanding of the processes at the electrode/IL interface is still at a preliminary stage. Herein, we employ electrochemical in situ scanning tunneling microscopy (STM) to investigate structural changes of a Au (111) single-crystal surface in four ILs: 1-butyl-1-methylpyrrolidinium dicyanamide [BMP] [DCA], 1-butyl-1-methylpyrrolidinium bis(trifluoromethane)sulfonimide [BMP][TFSI], 1-ethyl-3-methylimidazolium dicyanamide [EMIm][DCA], and 1-ethyl-3-methylimidazolium acetate [EMIm][OAc]. The STM data demonstrate a significant effect of IL ions on the potential ranges of Au(111) surface stability/instability and on the intensity and pattern of the occurring surface changes. Moreover, the effect of both the anion and cation on the surface stability is considerable in a wide range from high negative to high positive potentials. Apparently, not only strong ion adsorption but also the arrangement of IL ions at the electrolyte side of the interface has a significant impact on the stability of the gold surface.[a] Dr.

Interactions of the Ionic Liquid [C2C1Im][DCA] with Au(111) Electrodes: Interplay between Ion Adsorption, Electrode Structure, and Stability

“…In the next step, we probed the stability of the Au(111) surface in the presence of [C 2 C 1 Im]­[DCA]. Note that the chemical and physical properties, such as molecular structure, solubility, and conductivity of the IL, can have a direct effect on the electrochemical stability of the gold surface. − First, we start with cyclic voltammetry (CV). We designed the experiment (Figure a) in a way that we roughened the surface by oxidative and reductive cycles between 0.05 and 1.7 V RHE (200 mV·s –1 ) in the absence and presence of the IL.…”

Specific Cation Adsorption: Exploring Synergistic Effects on CO2 Electroreduction in Ionic Liquids

“…Further, in the case of Au, a well‐defined diffusion‐limited reduction peak does not develop prior to the onset of [BMIm] + reduction. In agreement with the literature, the overall slower reaction kinetics on Au can be associated with the extraordinarily high affinity of the [BMIm] + cations for Au and their resulting strong chemisorption on the electrode surface, which (partially) blocks reactive surface sites and thus limits the CO 2 RR.…”

Dataset of the electrochemical potential windows for the Au(hkl)|ionic liquid interfaces defined by the cut-off current densities

“…For instance, the decomposition of ILs can be significantly reduced by limiting the potential of the Au( hkl ) working electrode to within the E dl . These data can be used to gain further insights into the origin of each anodic or cathodic process occurring at Au( hkl )|IL interfaces by means of microscopic or spectroscopic techniques such as scanning tunneling microscopy [3] , [4] , [5] and differential electrochemical mass spectroscopy [6] . These data were analyzed at different j cut-off values, thereby providing a basis for a fair comparison of E dl and E pw between different electrode|IL interfaces.…”

“…These data can be used to gain further insights into the origin of each anodic or cathodic process occurring at Au( hkl )|IL interfaces by means of microscopic or spectroscopic techniques such as scanning tunneling microscopy [3] , [4] , [5] and differential electrochemical mass spectroscopy [6] .…”