Solid-state amperometric CO2 sensor using a sodium ion conductor

A solid-state amperometric CO2 sensor was prepared by combining a NASICON (Na+ conductor, Na3Zr2Si2PO12) with a porous Na2CO3 auxiliary layer deposited on a sensing electrode. The current between sensing and counter electrodes as a function of CO2 concentration was approximately linear in the range of 200–2000 ppm at 400 °C. The device could be operated stably during the test period (60 days). The sensing characteristics and long-term stability were discussed in the light of the sensing mechanism.