文摘
The molecular arrangement and surface dynamics of Au (111) electrodes in 1-hexyl-3-methylimidazolium chloride ([HMIm][Cl]) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIm][TFSA]) were investigated by in situ high-speed scanning tunneling microscopy (video-STM). These measurements provide direct insights into the potential-dependent adlayer structure of adsorbed [HMIm]+ cations and Cl– anions on the Au (111) surface. At low electrode charge densities highly dynamic structures with only local order are observed. After changing the potential in the negative direction, stripe-like adlayers structures are observed, which are attributed to [HMIm]+ in a planar adsorption geometry. These can be described by simple commensurate (√3 × 3) and a (√3 × √13) structures in the presence of Cl– and [TFSA]− counterions, respectively, indicating that the in-plane arrangement of the cations is affected by epitaxial effects and coadsorbed anions. Upon a further decrease in potential, a transition to a more close-packed (√3 × 2) adlayer phase is observed in [HMIm][TFSA], in which the cations are partly oriented away from the metal surface.