Development of In Situ Electrochemical Scanning Electron Microscopy with Ionic Liquids as Electrolytes

We report that ionic liquids (ILs) can be observed by electron microscopy without any charging of the liquid. Based on this, we present an in situ electrochemical scanning electron microscopy (in situ ECSEM) system. The key technology that enables in situ ECSEM is that charges can be removed from an IL by grounding it with a Pt wire, even if the IL is in an insulating glass cell. As a first demonstration, we describe the redox reaction of a polypyrrole (PPy) film accompanied by changes in its thickness when it is polarized by the film-deposited Pt electrode in the IL. Furthermore, energy-dispersive X-ray fluorescence (EDX) analysis can be employed for the electrode polarized in the IL. The component analysis by EDX of PPy in an IL containing K+ as a marker, reveals doping of electrolyte cations into the PPy film upon the latter's reduction and dedoping of cations from the film upon oxidation.