DETECTION OF CO2 USING A SOLID-STATE ELECTROCHEMICAL SENSOR-BASED ON SODIUM IONIC CONDUCTORS

The sensing characteristics of a solid-state electrochemical CO2 gas sensor, expressed as Pt\O2, Na2O\\Na ionic conductor\\Na2CO3\CO2, O2\Pt were investigated by a two-electron electrochemical reaction. The number of electrons for the cell reaction was higher than 2 and approached 2 with an increase in the operating temperature up to 500-degrees-C. The introduction of water vapor lowered the measured e.m.f. and increased the response time. The formation of sodium oxides in the Na2CO3 layer was considered as a possible cause of these water effects. Sensing characteristics recovered completely after the water vapor was removed. The lowering of the e.m.f. caused by water sorption was reduced by using a densified Na3Zr2Si2PO12.