Silver(I) chlorides speciation and its relationship to the design, construction and evaluation of true Ag(s)/[AgCln]1−n reference electrodes for their use in bis(trifluoromethylsulfonyl)imide room temperature ionic liquids

Abstract

This study describes a methodology for the design of true reference electrodes of the second kind based on the chemical speciation of the system AgCl(s)/[AgCln]1−n in both homogeneous and heterogeneous systems in bis(trifluoromethylsulfonyl)imide room temperature ionic liquids (RTIL), based on measurements of the open circuit potential (OCP) of Ag(s) or Ag(s)|AgCl(s) indicator electrodes immersed in solutions of Ag [NTf2] and [C2mim]Cl in RTIL, as well as on representative potentiometric titrations of Ag(I) or of chloride ions in the same media. The found values of the apparent equilibrium constants of the chemical equilibrium processes associated to the electrode potential at the metal|RTIL interface, lay the foundation for the design of true reference electrode systems. To test the usefulness of the information collected during the chemical speciation of these systems, four true reference electrodes were built for their use in four imidazolium-based bis(trifluoromethylsulfonyl) RTIL, and their electrode potentials were determined over time using the [Co(Cp)2]+/0 or [Fe(Cp)2]+/0 redox couples as internal redox references. The aim of this work is to provide a simple method for the development and characterization of true reference electrodes for their use in RTIL, thus averting the use of QRE and enabling the construction of comparable potential scales in RTIL.