Effect of Dry and Humidified Gases at Porous Electrolyte NOx Sensors

The impedancemetric technique was used to investigate the electrochemical behavior of NOx sensors composed of 4.6 mol.% Y2O3 – ZrO2 (PSZ) and 8 mol.% Y2O3 – ZrO2 (FSZ). Sensors were fabricated using ceramic processing methods. The impedance response indicated that: 1) PSZ based sensors demonstrated less cross-sensitivity to H2O in comparison to the FSZ based sensors, and, 2) the particle size of PSZ did not impact the cross-sensitivity to H2O. The activation energy for the FSZ based sensors changeds more substantially for dry versus humidified gas conditions, in comparison to that for PSZ based sensors. Impedance spectroscopy measurements were collected for PSZ and FSZ based sensors at different operating frequencies to understand the impact of H2O on the impedance response, NO sensing response, and sensors time response.