Mixed potential type ammonia sensor using Fe-substituted LaCoO3 sensing electrode prepared by flame spray pyrolysis

Abstract NH3 detection is of great significance for precise control of the SCR system. In this paper, mixed potential type ammonia sensor using LaCo1-xFexO3 sensing electrode, YSZ electrolyte, and Pt reference electrode was developed. LaCo1-xFexO3 sensing materials were made by flame spray pyrolysis technique, and Fe B-site substitution was implemented to enhance the sensing performance. It was observed that in the concentration range of 20–70 ppm at 475 °C, the sensor using LaCo0.9Fe0.1O3 as sensing electrode exhibited the highest sensing signal and sensitivity to ammonia among the LaCo1-xFexO3-SE sensors (x = 0, 0.05, 0.1, 0.2, 0.3). A sectional linear relationship between the response value change( Δ V ) of that sensor and the logarithm of ammonia concentration within the range of 2–15 ppm and 15–70 ppm was noticed, and the sensitivities were 17.52 and 87.22 mV/decade, respectively. Its lower detection limit reached 2 ppm at 475 °C. Its excellent sensing properties are ascribed to enriched oxygen vacancies and high electrocatalytic performance of the perovskite electrode. Moreover, the sensor exhibited good selectivity against CH4, CO, NO, NO2, and good stability against oxygen and water vapor concentration fluctuation. Besides, the sensing response to 50 ppm ammonia has been tested for 22 days and only a slight fluctuation within 7 % was observed. Furthermore, the mixed potential sensing mechanism of the sensor was discussed.