NASICON-based amperometric CO2 sensor using Na2CO3–BaCO3 auxiliary phase

An amperometric CO2 sensor was fabricated using a Pt|NASICON (Na+ conductor, Na3Zr2Si2PO12)|Pt cell and a porous Na2CO3–BaCO3 (1:1.7 in molar ratio) auxiliary layer. The sensor with the Na2CO3–BaCO3 layer showed a faster response than that with the Na2CO3 layer, and the sensor signal was barely influenced by the humidity. When operated in an amperometric mode with an applied external electric field, the sensor could detect the CO2 concentration stably and precisely without the need for a reference gas or a reference electrode material, and the sensor signal was constant for extended test periods (60 days). The sensing mechanism and the long-term stability is discussed in terms of the amperometric operation of the sensor.