Mining and industrial activities frequently emit toxic and harmful gases, such as sulfur dioxide, ammonia and carbon dioxide, which contaminate the environment and pose serious health risks. Consequently, real-time monitoring of these gases is essential for workplace and environmental safety. Although conventional techniques such as spectroscopy, chromatography, colorimetric sensing, and biosensing are widely used, they are often limited by high cost, bulky instrumentation, slow response, poor portability, and low selectivity.1 Electrochemical sensors have emerged as a promising alternative technique due to their low cost, portability, high sensitivity, and rapid response.
In recent years, room temperature ionic liquids (RTILs, or ILs for short) and their polymerised forms, poly(ionic liquid)s (poly(IL)s), have played a significant role in the development of modern electrochemical gas sensors.2 Their promising characteristics, such as good chemical and thermal stability, low volatility, and wide electrochemical windows,2 along with good intrinsic conductivity, tuneable physical properties, the mechanical stability of polymers, combined with the functional flexibility of different ions, makes poly(IL)s an attractive electrolyte material for commercial gas sensor applications.3 Despite these advantages, challenges remain, including electrode fouling, reference electrode potential drift, and cross-sensitivity.4
In this work, poly(IL)/IL mixtures have been investigated as promising gel-like, stable, and non-flowing films for electrochemical gas sensing. The experimental approach explores cation-anion combinations, by varying the cation with a constant anion, varying the anion with a constant cation, and varying both the IL and poly(IL), to tune sensor performance and selectivity. This study will present results on the electrochemical behaviour of gases such as, ammonia, oxygen, and sulfur dioxide, by systematically varying IL/poly(IL) ratios and gas concentrations, including the detection of binary gas mixtures. The electrochemical window of the IL/poly(IL) systems, along with film stability, electrode lifetime, and detection limits, will be discussed to highlight their suitability for stable and selective gas sensing applications.