Enhanced mixed potential NOx gas response performance of surface modified and NiO nanoparticles infiltrated solid-state electrochemical-based NiO-YSZ composite sensing electrodes

We have designed the solid-state electrochemical mixed potential type NiO and yttrium-stabilized zirconia (YSZ) composite based sensing electrode for selective detection of NOx at elevated temperatures. The planner NiO-YSZ composite sensing electrode could detect NOx even at 400 °C, with acceptable response/recovery rates. The change in emf values of the sensor varied linearly with NOx concentrations on a logarithmic scale in the range of 5-100 ppm. The response characteristic of the sensor was improved by modifying the surface with different vol% of pore former. As a result, obtained porous electrodes showed better response characteristics concerning speed and response owing to higher porosity. To improve response kinetics of porous NiO-YSZ electrode, NiO nanoparticles are infiltrated into an optimized NiO-YSZ sensing electrode surface by controlled urea/cation infiltration method. The experimental results demonstrated that NiO nanoparticles infiltrated NiO-YSZ sensor electrode reveal remarkably high emf response to NOx compared that of planar electrode, suggesting that NiO nanoparticles introduction can significantly enhance catalytic activity and electrochemical performance of NiO-YSZ electrode. Finally, the porosity effect of electrode subtracts (YSZ) with NOx gases response and recovery kinetics was examined under the optimum operating temperature at 400 °C. The sensing mechanism based on the mixed potential for the surface modified NiO-YSZ composite sensing electrode was discussed based on the obtained result of sensing characterizations.