Lightweight, Room-Temperature CO(2) Gas Sensor Based on Rare-Earth Metal-Free Composites—An Impedance Study

[Image: see text] We report a light, flexible, and low-power poly(ionic liquid)/alumina composite CO(2) sensor. We monitor the direct-current resistance changes as a function of CO(2) 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 CO(2) 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.