Viscosity and Ionic Conductivity of Imidazolium based Ionic Liquids bearing Triiodide Anion

Abstract

In the electrolyte application for dye sensitized solar cells, utilization of ionic liquids is getting the highlights to replace volatile organic solvent thanks to their low volatility, thermal and electrochemical stability. The iodide/triiodide redox electrolyte is the preferred choice for this application, hence numerous iodide-based ionic liquids have been explored and reported. On the contrary, the transport properties of triiodide based ionic liquid is often lack of reporting despite of having an equal influence on the overall viscosity and ionic conductivity of the electrolyte. In this study, three alkylimidazolium triiodide ionic liquids were synthesized from the respective alkylimidazolium iodide ionic liquids precursors and their physicochemical and conductivity properties are reported. 1H NMR analysis showed a slight shifting of position of the resonances of triiodide based alkylimidazolium ionic liquids as compared to their precursors due to less electronegativity nature of triiodide anion. The formation of triiodide-based imidazolium ILs have dramatically altered the transport properties in which the ionic liquids obtained are of low viscosity and high ionic conductivity.

Prediction of the conductivity and compatibility of the selected ionic liquids (ILs) with Nafion™ using COSMO-RS

“…This is in accord with the study reported in [12] where the incorporation of nitratebased ILs into the Nafion™ membrane has resulted in a greater conductivity of the membrane compared to the usage of formate-based ILs. The variation in length of the alkyl chain attached to the imidazolium-based showed that the longer alkyl chain caused the ionic conductivity to be lower as it induced greater intermolecular attractions and impedes ion mobility as reported in [18,[23][24][25][26]. The phosphonium and boron-based ILs showed significantly lower conductivities compared to the imidazolium and ammonium-based ILs.…”

“…Apart from that, the length of the alkyl chain of the imidazolium was also varied. Based on the predicted conductivities, the variation of the anion has a greater effect on the ionic conductivity of the resulting ILs [18,23]. The combination of nitrate anion followed by trifluoromethanesulfonate with all cations has resulted in the highest conductivity compared to other anions.…”