A carbon dioxide gas sensor based on solid electrolyte for air quality control

A practical CO2 gas sensor for air quality control is developed by using a combination of a Na3Zr2Si2PO12 (NASICON) as a solid electrolyte and Li2CO3 as a carbonate phase. The sensorʹs electromotive force (emf) shows a linear relationship with the logarithm of CO2 concentration. Zeolite is chosen as a filter material in order to minimize the effect of interfering gases on the sensorʹs emf and shows very little sensor response deterioration to CO2. Under continuous energizing, both the emf and a change in the emf (defined as Δemf) are stable over a period of 2 years. However, after the sensor is exposed to a high humidity atmosphere in an unpowered state, the emf decreases, but Δemf stays constant. A new data selection method for renewing the standard of the emf is investigated in order to monitor CO2 concentration using Δemf. The output of the CO2 monitor corresponds to a conventional non-dispersive infrared (NDIR) analyzer.