Novel high-selectivity NO2 sensor incorporating mixed-oxide electrode

Solid-state planar sensor using scandia-stabilised zirconia (8 mol% Sc2O3–ZrO2) solid electrolyte and CuO + CuCr2O4 mixed-oxide sensing electrode has been tested in NO2 containing gaseous atmosphere in the range of 10–500 ppm NO2 between 518 and 659 °C. The sensor has been found to respond consistently and rapidly to change in concentration of NO2 in the oxygen rich gas mixture at 659 °C. At 659 °C, a logarithmic relationship between the measured electromotive force (EMF) and NO2 concentration from 100 to 500 ppm has been observed whereas a linear relationship between EMF and NO2 concentration has been observed below 30 ppm. The sensor showed negligible cross-sensitivity to O2, CO and CH4 in the gas stream at 659 °C. A possible sensing mechanism has been discussed.