Sensing characteristics of mixed-potential-type zirconia-based sensor using laminated-oxide sensing electrode

A planar sensor was fabricated using a yttria-stabilized zirconia (YSZ) plate and laminated-oxide sensing electrode (SE) aiming for selective detection of NO2 at high temperature. The NO2 sensing characteristics as well as the cross-sensitivity to various gases were examined in the temperature range of 700–900 °C under the wet condition (5 vol.% H2O). It was found that the sensor attached with the laminated hetero-oxide layer (Cr2O3/NiO (+WO3)) could detect NO2 selectively at 895 °C. It was speculated that the additional oxide layer (Cr2O3) placed on the NiO (+WO3) layer acted as a catalyst for the oxidation of CO, hydrocarbons and NO, and then led to better NO2 selectivity.