Local analyses of ionic liquid/solid interfaces by frequency modulation atomic force microscopy and photoemission spectroscopy

Local analyses of ionic liquid/solid electrode interfaces at a controlled electrode potential are of fundamental importance to understanding the origin and properties of the electric double layer at the interfaces, which is necessary for their application to electrochemical devices. This account summarizes our recent achievements of such analyses by using the novel analytical tools of electrochemical frequency modulation AFM (EC-FM-AFM) and electrochemical photoemission spectroscopy (EC-PES). Rather stable stepped structures composed of layers of ion pairs and softer solvation layers outside of the imaged layer were clearly visualized by FM-AFM depending on the substrates. An extremely extended diffusion layer was directly observed by EC-PES during the electrodeposition of metal ion solutes.