Sensitivity and selectivity enhancement of the YSZ-based mixed-potential ammonia sensors with flame-spray-made double-sensing electrodes
YSZ-based mixed-potential sensors with double-sensing electrodes were fabricated for ammonia (NH 3 ) detection. ZnO and LaCoO 3 nanoparticles prepared by flame spray pyrolysis (FSP) method were used as the sensing materials. The sensing responses of ZnO and LaCoO 3 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 NH 3 at 450, 475, 500, 525 ℃ , respectively. Moreover, the NO 2 interference effects on NH 3 detection of ZnO and LaCoO 3 electrodes were opposite and can be counteracted based on the double-sensing-electrode structure, eliminating most of the cross-sensitivity to NO 2 . The double-sensing-electrode sensor exhibited good performance under CO, CH 4 , NO, NO 2 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 NH 3 sensors could be enhanced to a higher level.
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