Solid electrolyte CO2 sensor using NASICON and perovskite-type oxide electrode

Solid-state electrochemical sensor devices combined with sodium super ionic conductor (NASICON: Na1+xZr2SixP3−xO12) discs and perovskite-type oxide electrodes have been developed for the detection of CO2 in the range of 100–2000 ppm. Among the various sensor devices tested, Co-based perovskite-type oxide electrodes were found to show excellent sensing properties to CO2 at 200–300°C. Especially, NdCoO3- and La0.8Ba0.2CoO3-based elements showed the best CO2 sensing properties, i.e., the sensor response (EMF) was almost linear to the logarithm of CO2 concentration in the range between 100 and 2000 ppm, the response time to 500 ppm CO2 was as short as 1–2 min. An open-reference electrode type sensor element, which fitted with NdCoO3 and La0.8Pb0.2CoO3 for sensing and reference electrodes, respectively, showed excellent CO2 sensing properties and hardly affected with oxygen partial pressure.