Ionic liquids combined with Pt-modified ordered mesoporous carbons as electrolytes for the oxygen sensing

Abstract

In recent years, room temperature ionic liquids (RTILs) have been highly utilized in electrochemical fields. Specifically, ionic liquids (ILs) as electrolytes augur promising potential for the next generation of advanced and miniaturized electrochemical gas sensors. In this paper, 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]), 1-propyl-3-methylimidazolium hexafluorophosphate ([PMIM][PF6]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) were synthesized through a facile one-pot method. We found that [EMIM][PF6] and [PMIM][PF6] exist in the solid state at room temperature. Hence, these ILs can effectively avoid the leakage of electrolytes. However, [BMIM][PF6] can be present in liquid state at room temperature as the melting point decreases, due to the increasing of alkyl chain (Cn, n<6) for the ILs. Compared to solid electrolyte gas sensors, sensors based on liquid electrolytes offer a reliable response and achieve sufficient ion mobility to sense oxygen. Our work provides an incentive to enhance the properties of a liquid electrolyte by mixing it with Pt-modified ordered mesoporous carbons (Pt-OMCs), which not only prevents the aggregation of OMCs but also provides a large number of active sites for oxygen reduction. The limit of detection (LOD) in oxygen sensors based on Pt/CMK-3-COOH-[BMIM][PF6] is relatively low (1.10% O2). Our results indicate that the synergistic combination of ILs and Pt-OMCs markedly promotes the performance of electrochemical oxygen sensors.