Underpotential Deposition of Silver on Au(111) from an Air‐ and Water‐Stable Ionic Liquid Visualized by In‐Situ STM

Abstract

There is a steadily increasing interest in room-temperature ionic liquids (ILs) as media for metal electrodeposition. However, the fundamental understanding of the underlying surface processes at the electrode/IL interface and of the initial stages of electrodeposition is still at a very preliminary stage. In this article, we investigate the underpotential deposition (upd) of Ag on a welldefined Au(111) single crystal surface from an air-and waterstable IL, 1-butyl-1-methylpyrrolidinium dicyanamide [BMP] [DCA]. By employing in-situ scanning tunneling microscopy (STM), we could visualize individual stages of the Ag upd process as a function of the applied electrode potential and correlate voltammetric responses to the obtained STM data. The initial Ag upd process results in the formation of an Ag-(4 × 4) lattice, which is further transformed into a pseudomorphic Ag-(1 × 1) monolayer at the underpotential of~40 mV. The structural stability of the Au(111) surface in [BMP][DCA] is also examined in the absence of Ag + ions in both the negative and positive potential regions.[a] Dr.

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

“…One can see that the Au(111) surface is irreversibly changed: small gold islands disappear; the terraces become uneven; the finger‐like islands attached to the steps become fuzzier. It should be noted that these changes occur in [EMIm][DCA] at ∼0.40 V more positive potentials than in [BMP][DCA] as well as in [BMIm][DCA] (see our previous reports) . This result is remarkable, as it indicates a strong effect of the cation on the surface etching at rather positive potentials, where predominant adsorption of anions would be expected.…”

“…One can see that the Au(111) surface is irreversibly changed: small gold [DCA] (see our previous reports). [37][38] This result is remarkable, as it indicates a strong effect of the cation on the surface etching at rather positive potentials, where predominant adsorption of anions would be expected.…”

“…Previously, [37][38] we showed that the Au(111) electrode surface in [BMP][DCA] is not subject to any restructuring or etching at potentials between À 0.34 V and 0.50 V. However, our STM data demonstrated surface etching and formation of pits on the (111) terraces at the potentials above 0.50 V. This etching is accompanied by a drastic growth of the anodic current (see Figure 2a), indicating electrochemical dissolution of gold. In the reverse scan, the cathodic peak at~0.5 V corresponds to redeposition of gold (in agreement with [40]).…”

“…Despite the findings in the above‐mentioned publications on the etching of the Au(111) electrode surface, there is yet no clear explanation of this phenomenon. However, all studies relate this behavior to strong interactions between IL cations such as [EMIm] + , [BMIm] + (1‐butyl‐3‐methylimidazolium), or [BMP] + (1‐butyl‐1‐methylpyrrolidinium) with the gold surface, which causes a weakening of Au−Au bonds and an enhancement of Au surface atom mobility . No possible effect of IL anions on the surface restructuring is considered in these reports, while a recent computational analysis showed that the nature of the anion plays an important role in the altering of the interfacial interactions between ILs and the gold surface.…”

Structure‐Sensitivity and Electrolyte Effects in CO2 Electroreduction: From Model Studies to Applications

“…A feasible, less explored method to electrodeposit nanostructures is the use of ILs . ILs usually show chemical and transport properties that allow calibrating the growth, size and shape of the particles . In that way, ILs could be used not only as co‐catalysts of the CO 2 RR, but also for nanocatalyst design.…”