<i>In situ</i> ATR-SEIRAS Studies on Ionic Liquid/Electrode Interface under Metal Electrodeposition

The origin of the characteristic overpotentials for electrochemical deposition of metals in ionic liquids are discussed with the viewpoint of the role of the interfacial structure of ionic liquids on electrodes. For this purpose, we developed a novel method for deriving interfacial information by using surface-enhanced infrared absorption spectroscopy (SEIRAS) even under electrochemical deposition that modifies the substrate structure. In-situ interfacial measurement by using this method revealed that onset potential of Co electrodeposition is identical to that for the anion-cation replacement in the first ionic layer on the electrode. This can be explained by including interfacial charge-ordered structure into Marcus theory.