Effect of Humidity and Impurities on the Electrochemical Window of Ionic Liquids and Its Implications for Electroanalysis

Replacing conventional aqueous-based electrolytes with room-temperature ionic liquids (RTILs) for electrochemical applications is a major research focus. However, in applications where RTILs are exposed to real-world environments, their hygroscopic nature affects their promising physicochemical properties, such as broad electrochemical windows (EWs) and high chemical stability. In this study, the electrochemical windows of nine commercially available RTILs have been determined on platinum thin-film electrodes in "dry"conditions (4.3-6.5 V) via cyclic voltammetry, and a systematic study over a wide humidity range (relative humidity (RH) between 95%) has been carried out. A significant reduction in the EW occurs even at low moisture contents (