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The surface interaction of two air- and water-stable ionic liquids (ILs), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonylamide (EMImTFSA) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl)sulfonylamide (BMPTFSA), with Au(111) has been investigated using atomic force microscopy (AFM), cyclic voltammetry, and scanning tunneling microscopy (STM) measurements. AFM experiments reveal that multiple solvation layers are present at the gold interface for both ILs and that the strength of the interaction between the innermost layer and the substrate is dependent on the cation type; the force required to rupture the innermost solvation layer is greater for BMPTFSA than for EMImTFSA, attributed to stronger cation surface interactions. In situ STM elucidates the influence of IL species on restructuring of the Au(111) interface. In the presence of BMPTFSA, the Au(111) surface restructures to produce a wormlike pattern, but this unusual morphology is not observed for the EMImTFSA−Au(111) system. This remarkable difference in electrochemical behavior is ascribed to the greater strength of the interaction of BMP + compared to EMIm + with the Au(111) surface. These results demonstrate that such interfacial effects have to be considered for all electrochemical reactions and provide insight into the electrical double-layer structure in IL systems.
Atkin et al. (Wed,) studied this question.