Mixed potential NH3 sensor with LaCoO3 reference electrode

Mixed potential NH3 sensors using an yttria stabilized zirconia (YSZ, 8 mol% Y2O3) electrolyte were prepared and evaluated at 700 °C. Various oxide materials were tested as a sensing electrode, among which In2O3 sensing electrode showed the highest sensitivity to NH3 with good stability. However, the EMF of the sensor decreased to 50% of its original value when 150 ppm NO2 was added to gas containing NH3. In an effort to eliminate interference from NO2, a new concept of a mixed potential sensor using an oxide reference electrode of LaCoO3 instead of a noble metal is introduced. It was found that the interfering effect of the new sensor to 150 ppm NO2 was reduced from 50% to 10%. The EMF showed little change upon exposure to 1000 ppm CO and 150 ppm NO with a logarithmic dependence of the EMF on the NH3 concentration.