Influence of water on the electrochemical characteristics and nanostructure of Bi(hkl)│Ionic liquid interface

Abstract

In electrochemical applications of ionic liquids (ILs), the presence of residual amounts of water can influence the performance of ILs as electrolytes when developing novel electrochemical devices. In this work, the influence of water additive on the electrical double layer formation and adsorption of ions from 1-ethyl-3-methylimidazolium trifluromethanesulfonate IL at semi-metallic bismuth single crystal electrodes has been studied via cyclic voltammetry, electrochemical impedance spectroscopy, and in situ scanning tunneling microscopy methods. Major differences in water-adsorbed IL mixtures are observed at bismuth single crystal electrodes within a wide potential region: increased current densities and anomalous capacitance maxima, especially at positive polarization conditions. The kinetics of adsorption layer formation significantly are strongly affected by the adsorption processes of both cations and anions under polarization conditions, shown by the characteristic relaxation time constant results. Interfacial distribution of ions and surface nanostructure is visualized at the atomic resolution under in situ scanning tunneling microscopy study. These results provide a detailed understanding of the Bi(hkl) surface structure and the ion adsorption processes dependence on electrode polarization.