Solid Electrolyte Carbon Dioxide Sensor Using Sodium-Ion Conductor and Li2CO3-BaCO3 Electrode

Abstract
A sodium-ion conductor (Na3Zr2Si2PO12: NASICON)-based CO2 sensor using a Li2CO3-BaCO3 electrode responded very well to CO2 in air over a wide temperature range of 270-600°C. The sensor responses, electromotive force (EMF), to varying partial pressure of CO2(P CO2 ) were in accordace with a 2-electron reaction of CO2. On the other hand, the sensor response to a fixed P CO2 (2×10-3 atm) was almost independent of partial pressure of O2(P O2 ) at temperatures above 450°C, while at 305°C and below, it depended on P O2 in a manner similar to a 2-electron reactionof O2. Thus, two types of sensing electrode reactions were indicated to occur depending on working temperature.