Ionic Liquid-Functionalized CNT Electrochemical Platform Governed by a Dual-Path Sensing Mechanism for Versatile VOC Detection

Abstract Room-temperature ionic liquids (RTILs) have garnered significant attention as advanced electrolytes for electrochemical gas sensors owing to their negligible volatility and wide electrochemical windows. However, their application in detecting volatile organic compounds (VOCs) is constrained by high viscosity (limiting mass transport) and the sluggish electrooxidation kinetics of most VOCs. Supported ionic liquid phase (SILP) materials, which immobilize RTILs on porous supports to amplify the gas–liquid interface, present a promising yet underexplored avenue for addressing these challenges. Herein, we develop a novel electrochemical platform configured with high-purity semiconducting carbon nanotube (CNT) films serving as both working electrodes and scaffolds to immobilize RTILs to construct a nanostructured SILP electrolyte. This architecture simultaneously maximizes the active gas–liquid interface, minimizes the gas diffusion distance, and ensures efficient charge transport. The platform enables quantitative detection of ethanol and isopropanol, exhibiting well-defined linear responses from 0–800 ppm and 0–600 ppm, respectively, with distinctive non-monotonic patterns at higher concentrations. Mechanistic investigations reveal that the sensing process diverges from conventional faradaic electrochemistry and is instead governed by a dual-path mechanism: competitive adsorption between oxygen and VOC molecules at the SILP surface, coupled with VOC absorption into the bulk phase. This unique mechanism, which circumvents the limitations of direct electrooxidation by exploiting distinct interactions between VOCs and the SILP, provides inherent discriminative capability. Consequently, our work establishes the CNT-SILP system as a versatile, miniaturization-ready platform for room-temperature VOC sensing and paves the way for novel intelligent gas sensors.