Ce incorporated pyrochlore Pr2Zr2O7 solid electrolytes for enhanced mild-temperature NO2 sensing

NO2 sensor has attracted extensive attention due to its important application in environment monitor. Conventional NO2 sensors based on the yttria-stabilized zirconia (YSZ) electrolyte possess fast response, high sensitivity and good stability, whereas its ionic conductivity decreases significantly at low- and intermediate-temperature, limiting the practical application in motor vehicles. In this work, a pyrochlore-phase A2B2O7 solid electrolyte, Pr2Zr2−xCexO7+δ (PZC), was applied for the first time to construct the amperometric-type NO2 sensor. Ce incorporated significantly improved the sensing performance of the PZC NO2 sensor with NiO as the sensing electrode. The effect of Ce-doped concentration and operating temperature on the sensitivity, selectivity, stability, response and recovery characteristics were investigated in detail. The results showed that the optimal sensor based on the Pr2Zr1.9Ce0.1O7+δ substrate gave high sensitivity, excellent selectivity and quick response-recovery behavior to NO2 gas. The gas-sensing mechanism was also discussed. The PZC sensors are well established effective for sensing NO2 at mild-temperature working window of 500-700 °C, and thus exhibit the promising application in motor vehicles.