Sensitivity and selectivity enhancement of the YSZ-based mixed-potential ammonia sensors with flame-spray-made double-sensing electrodes

Abstract

YSZ-based mixed-potential sensors with double-sensing electrodes were fabricated for ammonia (NH3) detection. ZnO and LaCoO3 nanoparticles prepared by flame spray pyrolysis (FSP) method were used as the sensing materials. The sensing responses of ZnO and LaCoO3 sensing electrodes can be overlapped based on the double-sensing-electrode structure, thereby significantly enhancing the sensitivity compared with the traditional mixed-potential sensors using Pt reference electrode. The sensitivities of this sensor reached up to -102.85, -75.312, -70.165, -48.616 mV/decade to 10–50 ppm NH3 at 450, 475, 500, 525 ℃, respectively. Moreover, the NO2 interference effects on NH3 detection of ZnO and LaCoO3 electrodes were opposite and can be counteracted based on the double-sensing-electrode structure, eliminating most of the cross-sensitivity to NO2. The double-sensing-electrode sensor exhibited good performance under CO, CH4, NO, NO2 interference, oxygen fluctuation, and humidity variations, and showed good long-term stability. The results of sensing performance exhibited the sensors with double-sensing electrodes have a great potential for application on SCR system of diesel engines. In further studies, each sensing electrode can be optimized respectively and the sensitivity and selectivity of NH3 sensors could be enhanced to a higher level.