An Amperometric Type NO2 Sensor Utilizing La0.7Sr0.3MnO3-δ-NiO Composite Sensing Electrode

NO2 is an important pollutant of automobile engines and industrial fuels, making it important to quantitatively monitor and control. An amperometric-type NO2 gas sensor was fabricated using yttria-stabilized zirconia (YSZ) electrolyte with a bi-layered structure and La0.7Sr0.3MnO3-δ-xNiO (LSMO-xNiO, x=0-0.75) composite sensing electrode (SE) prepared by impregnation method in combination with self-demixing. The samples were characterized using SEM, XRD, and XPS, and their performance as sensors was tested. LSMO-xNiO composite SE particles were formed by de-mixing in the process of treating the precursor at high temperatures and are uniformly dispersed in the YSZ porous backbone. With the increase of NiO content, the SE particles become significantly large. At 450-600°C, the response currents at a fixed potential have a linear relationship with the NO2 concentrations at 25-700 ppm. Combining stability and sensitivity, the voltage was fixed to -0.25V. The introduction of NiO into the LSMO sensing electrode effectively improves the performance of the sensor. The sensor based on LSMO-0.5NiO has the highest sensitivity (0.0405 µA/ppm) at 550°C. Simultaneously, the sensor exhibits good anti-interference ability for CH4, CO2, O2, and NO, but has obvious cross-sensitivity to H2 and NH3. In addition, the response current of the sensor change with the increase of RH.