Electrochemical detection of SO2 in a hydroxyl functionalized and eutectic-based ionic liquid

Abstract

Using ionic liquids (ILs) as electrolytes in developing electrochemical sensors for SO2 detection is of much interest. We compared the electrochemical behaviors of SO2 in choline chloride–ethylene glycol-based deep eutectic solvent (ChCl–EG-based DES), 1-(3-hydroxypropyl)-3-methylimidazolium tetrafluoroboride ([C3OHmim]BF4), and [C3OHmim][Formula: see text]monoethanolamine (MEA) (6.2:1 in molar ratio). Addition of MEA into [C3OHmim]BF4 can significantly increase the SO2 absorption capacity and enhance the electrochemical response of SO2. However, as we use ChCl–EG-based DES, the reduction current is 10 times larger than in [C3OHmim]BF4 and 4 times larger than in [C3OHmim][Formula: see text]MEA (6.2:1 in molar ratio). And SO2 gas shows high diffusion coefficient value as in the ChCl–EG-based DES. A good linear relationship between the reduction current and the SO2 content was obtained in the tested SO2 gas content range from 200[Formula: see text]ppm to 1500[Formula: see text]ppm. Our findings provide new route for DESs as electrolytes for SO2 sensor designing with high sensitivity.