Electrochemical scanning tunnelling microscopy (EC‐STM) study of silver electrodeposition from a room temperature molten salt

Abstract

They are mainly composed of AICl3 and an organic salt [5] and show, depending on the Lewis acidity, wide electrochemical windows, which are sufficient to investigate the electrodeposition of most elements. In this short communication we report for the first time on the example of a simple model system (silver electrodeposition from an acidic AIC13/l-methyl-3-butyl-imidazolium chloride mixture, see also [6]), that EC-STM can be performed in molten salts: atomic resolution is achieved and processes during electrodeposition/electrodissolution can be viewed as a function of time. First examples of this observation are demonstrated.Preliminary results by in situ EC-STM on the electrodeposition of silver on highly oriented pyrolytic graphite (HOPG) from a room temperature molten salt are presented. The molten salt was composed of 55 mol-% AlCl, and 45 mol-% I-methyl-3-butyl-imidazolium chloride this mixture is liquid at ambient temperatureand contained AgCl in a concentration of 0.025 mol/l. The results show for the first time that HOPG can be imaged at this interface with atomic resolution and that the silver deposition/dissolution process can be viewed in situ.

The Electrode/Ionic Liquid Interface: Electric Double Layer and Metal Electrodeposition

“…The rapid development of in situ STM since 1990 has enabled investigations of electrode processes at electrode/electrolyte interfaces with unprecedented structural detail, and has thus played a vitally important role in advancing surface electrochemistry in aqueous solutions in the past two decades. [62,63] STM application in ionic liquids was initiated by Endres and Freyland et al in 1997, [64] for the investigation of Ag on highly oriented pyrolytic graphite (HOPG) in a chloroaluminate ionic liquid. In 2003, Mao and co-workers started to investigate the reconstruction and restructuring processes of Au single-crystalline electrode surfaces in a neat non-chloroaluminate alkylimidazolium-based ionic liquid.…”

“…[65] These works are representative of the initial stages of in situ characterization of interfacial electrochemistry in ionic liquids. Despite difficulties in achieving high-resolution STM images in ionic liquid, atomic- [64,66,67] and molecular-resolution [22,29,68,69] imaging has been achieved for some systems.…”

“…So far, only a few in situ STM studies in ionic liquids [29,64,66,68] have reached atomic or molecular resolution. Nevertheless, the adsorption of solvent molecules has been studied in neat ionic liquids with molecular resolution.…”

Electrochemically controlled self-assembled monolayers characterized with molecular and sub-molecular resolution

“…STM molecular images in organic solvents have also been reported, 112,113 but aqueous solution is the environment that dominates in situ STM investigations as well as the natural environment for biological macromolecules retaining their structure and function. The quality of lab water has now reached a level where the cleanness is in fact comparable with that in an UHV-environment, in the sense that the level of organic and inorganic impurities in the water compares with the residual pressure in UHVenvironment.…”

“…In situ STM can, however, be extended to other environments such as ionic liquids 113,[164][165][166][167][168] and organic solvents. These alternative environments can offer, for example much wider working potential windows as well as a wealth of thiols with all sorts of functional groups.…”