Deep eutectic solvent (DES)/O2 as an electrochemical indicator for acidic groups in the solid polymer electrolytes

• Published in: Journal of molecular liquids Vol. 319; p. 114144
• Main Authors: Karimi, Mohammad Bagher, Mohammadi, Fereidoon
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2020
• Subjects: Deep eutectic solvents; Electrochemical indicator; Polymer electrolyte membrane; Polymer electrolyte membrane; Deep eutectic solvents; Electrochemical indicator
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2020.114144

This study was launched to evaluate the potential use of a new class of ionic liquids called deep eutectic solvent (DES) for acid detection in solid polymer electrolytes (SPE) and nanoparticles by spontaneous electrochemical reaction. Sodium iodide (NaI) based DESs were thus prepared and employed as acid indicator for sulfonic acid groups of Nafion which is a semicrystalline polymer. The DESs were prepared with NaI as hydrogen bond acceptor (HBA) and ethylene glycol (EG) as hydrogen bond donor (HBD) in different molar ratios. The synthesized DESs were then characterized in terms of thermal transition behavior and rheological properties. The obtained results revealed that an electrochemical reaction might occur between sulfonic acid groups of Nafion and DES in presence of O2 resulting in Iodine (I2) formation in the DES with consequent appearance of a red-brown color. Therefore, the NaI based DES, due to its ability to dissociate protons from acidic groups and its consequent participation in electrochemical reaction to produce a coloring agent, can be considered as an acid indicator for SPEs and/or nanoparticles. •Iodide based deep eutectic solvents were investigated as acid indicator.•Deep eutectic solvents can be considered as fast and cheap indicators in solid polymers.•Interaction of deep eutectic solvents and acidic groups causes formation a coloring agent.•Deep eutectic solvents can be considered and fast and cheap indicators in solid polymers.•Deep eutectic solvent can be considered as acid indicator for nanoparticles.