An impedancemetric NH3 sensor based on Ag nanoparticle decorated NiFe2O4 sensing electrode prepared by electrochemical exsolution method

An impedancemetric NH3 sensor was prepared using Yttria-stabilized zirconia (YSZ) as the solid electrolyte and Ag nanoparticle decorated NiFe2O4 (NiFe2O4/Ag) prepared by electrochemical exsolution as the sensing electrode (SE). The feasibility of electrochemical exsolution was confirmed by XRD and TEM characterization. After a voltage of -2 V was applied across the sensor based on NiFe2Ag0.05O4.025 for 1000 s, a large number of Ag nanoparticles as the second phase appear on the surface of the NiFe2O4 particles and attached to the matrix. The effects of exsolution time, temperature, and voltage on the sensing performance of the sensor were investigated. After electrochemical exsolution, the response value and sensitivity of the sensor are significantly improved compared to the sensor before exsolution and the limit of detection (LOD) of the sensor is reduced from 50 ppm to 10 ppm at 500°C. In addition, the reproducibility of the electrochemical exsolution is good, and the sensor exhibits good stability. More importantly, the immunity of the sensor to NOx is significantly improved using the electrochemical exsolution SE.