Effects of Water on Electrochemical Behavior of ZnCl2 and FeCl3 in Deep Eutectic Solvent Composed of Choline Chloride and Urea
Feng Zhu, Runxu Deng, Qinglin Jiang
Abstract
Deep eutectic solvents (DESs) are promising as solvents and electrolytes in electrochemistry due to low volatility, wide electrochemical window, moderate ionic conductivity and solubility to some species. Water content has profound effects on physico-chemical properties of DESs and could be used to tune electrochemical performance of redox active species in DESs. Effects of water content on reline (mixture composed of choline chloride and urea in molar ratio of 1 : 2) were investigated, including ionic conductivity, electrochemical stability of reline and electrochemical processes of ZnCl2 and FeCl3 in reline. The experimental results showed, the ionic conductivity of reline is sensitive to water, when water content is below 41.0 wt %, and ionic conductivity keeps stable above 51.0 wt % water content. When water content changes from 41.0 to 51.0 wt %, transition point from “water-in-reline” to “reline components-in-water aqueous solvent” was observed from both electrochemical stability tests and electrochemical behavior of ZnCl2. Electrochemical processes of ZnCl2 and FeCl3 in reline are promoted with water content increase until up to 41.0 wt %.