Study on Sulfonic Acid Functional Group Modified Imidazole Ionic Liquids for Oxygen Concentration Detection

Abstract

The ionic liquid is a kind of ionic salt capable of being liquid state at room temperature. As a new type of green organic solvent, ionic liquid has the advantages of good electrical conductivity, wide electrochemical window, very low vapor pressure, and is widely used in electrochemical, organic synthesis and other fields. The use of ionic liquids as electrolytes in electrochemical oxygen sensors can alter the shortcomings of the current sensor's inability to operate at high temperature and humidity conditions. Besides, ionic liquids with certain catalytic functional group could improve the response performance of sensing devices. Therefore, in this paper, ionic liquids based on imidazolium, 1-methyl-3-propanesulfonic acid imidazolium hydrogensulfate ([Psmim]HSO4) and 1-methyl-3-butpropanesulfonic acid imidazolium hydrogensulfate ([Bsmim]HSO4 )with sulfonic-acid catalytic functional group were studied. Both ionic liquids mentioned above were synthesized through a traditional two-step method. Electrochemical tests including linear scanning voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) of both ionic liquids were carried out with an electrochemical workstation to characterize the intrinsic electrochemical performance of both ionic liquids. On the other hand, cyclic voltammetry (CV) curves were tested, which shows a proportional linear relationship between oxygen reduction peak current and the oxygen concentrations from 0% to 100% O2 with the corresponding R2 (R2 >0.97), and chronoamperometric current tsests were also carried out to futher confirm the ionic liquids promising materials for oxygen sensing. (This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.)