Lightweight, Room-Temperature CO₂ Gas Sensor Based on Rare-Earth Metal-Free CompositesAn Impedance Study

We report a light, flexible, and low-power poly­(ionic liquid)/alumina composite CO₂ sensor. We monitor the direct-current resistance changes as a function of CO₂ concentration and relative humidity and demonstrate fast and reversible sensing kinetics. Moreover, on the basis of the alternating-current impedance measurements we propose a sensing mechanism related to proton conduction and gas diffusion. The findings presented herein will promote the development of organic/inorganic composite CO₂ gas sensors. In the future, such sensors will be useful for numerous practical applications ranging from indoor air quality control to the monitoring of manufacturing processes.