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

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.