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

Abstract

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.

New Frontiers in Materials Science Opened by Ionic Liquids

“…These polymers physically deform when they undergo an oxidation/reduction cycle in an electrolyte solution because of doping/dedoping of cations in the PILE. Ding et al [251] and Arimoto et al [252] have succeeded to reveal the mechanism by the use of electrochemical techniques and an in situ electrochemical SEM system with energy-dispersive X-ray fluorescence spectroscopy (EDX), respectively. A PANI-based soft actuator device shows fast switching speed in BuMeImBF 4 and showed no failure after 1 million cycles under ambient conditions.…”

“…[289] A possibility of in situ observation of chemical reactions in ILs with an electron microscope was reported by our group. [252,290] The first example was a PPy film deposited on a Pt electrode (PPy j Pt electrode), redox of which is accompanied by changes in film thickness due to doping and dedoping of electrolyte ions. This electrode and a counter electrode were immersed in BuMeImTf 2 N and the cell was set in a vacuum chamber of an SEM so as to observe the cross-section of the PPy film.…”

“…Polymer-in-ionic-liquid electrolytes (PILEs), which are composed of an IL and p-conjugated polymers such as PANI (PAn), [238] PPy, [238,[250][251][252] and PT, [238,253] can be employed for the fabrication of lightweight, highly efficient electrochemical mechanical actuator devices. These polymers physically deform when they undergo an oxidation/reduction cycle in an electrolyte solution because of doping/dedoping of cations in the PILE.…”

Introduction of Ionic Liquid to Vacuum Conditions for Development of Material Productions and Analyses

“…If this is correct, it is possible to observe the reactions by an electron microscope. 13,14 We attempted to prove this possibility with SEM observation of electrochemical Ag deposition. For this purpose, we designed an electrochemical cell having a specific figure, as shown in Fig.…”

High-throughput CW-IR laser deposition and laser microscope imaging of binary ionic liquids in vacuum

“…The low vapor pressure of ILs allows their characterization [3] and processing [4,5] using high-vacuum techniques. In our previous works, we developed a new deposition technique of ILs in vacuum using a continuous-wave infrared (CW-IR) laser to prepare nanoscale IL droplets and thin films on a substrate without any decomposition [6], and also demonstrated that IL nanodroplets can be used as microreactors for crystal growth in vacuum [7].…”