Sensing Performance of a YSZ-Based Electrochemical NO₂ Sensor Using Nanocomposite Electrodes

An electrochemical NO2 sensor is fabricated using yttria-stabilized zirconia as electrolyte and SnO2-NiO nanocomposites as sensing electrodes. The SnO2-NiO nanocomposites with varying molar ratio (Sn:Ni = 1:3, 1:1, 3:1) were synthesized by a citric acid-assisted hydrothermal route and sintered over a YSZ-electrolyte to form the sensing electrode of the sensor. The phase structure and morphology of the electrodes were characterized by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) techniques. The NO2 sensing performance of the fabricated sensor was measured at 700°C with varying NO2 and O2 concentrations. Furthermore, the electrochemical polarization curves were studied for the analysis of the sensing mechanism. It was found that the sensing response (ΔV), sensitivity, response/recovery dynamics as well as cross-sensitivity of these sensors were greatly dependent over the cationic molar ratio (Sn: Ni) of the nanocomposite sensing electrode. Moreover, the SnO2-NiO nanocomposites displayed high sensitivity, high stability and low cross-sensitivity; projecting it as a potential sensing electrode material for the electrochemical NO2 sensors.