Mixed-potential type N2O sensor using stabilized zirconia- and SnO2-based sensing electrode

A stabilized zirconia-based electrochemical device attached with an oxide electrode was developed for monitoring nitrous oxide (N2O) in air at elevated temperatures. Among the 11 kinds of monoxides tested for a tubular zirconia device, SnO2 was found to exhibit the best sensing electrode properties, giving a relatively high sensitivity to N2O in air at 475°C. The electromotive force (emf) value of the device was almost linear to the logarithm of N2O concentration in the range of 50–200 ppm. The addition of a foreign oxide (e.g. Bi2O3 and Sm2O3) to SnO2 was effective to improve the N2O sensitivity. Especially the element using Sm2O3 (0.5 wt.%)–SnO2 sensing electrode exhibited the N2O sensitivity about 1.5 times as high as that using the pure SnO2 electrode, allowing to detect about 35 ppm N2O in air. On the basis of the measurements of anodic and cathodic polarization curves, the sensing mechanism was confirmed to involve a mixed potential at the sensing electrode.