SOLID ELECTROLYTE CARBON-DIOXIDE SENSOR USING SODIUM-ION CONDUCTOR AND LI2CO3-BACO3 ELECTRODE

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-degrees-C. The sensor responses, electromotive force (EMF), to varying partial pressure of CO2(P(CO2)) were in accordance with a 2-electron reaction of CO2. On the other hand, the sensor response to a fixed P(CO2)(2 X 10-3 atm) was almost independent of partial pressure of O2(PO2) at temperatures above 450-degrees-C, while at 305-degrees-C and below, it depended on P(O2) in a manner similar to a 2-electron reaction of O2. Thus, two types of sensing electrode reactions were indicated to occur depending on working temperature.