High-temperature ammonia sensor employing BaZr0.8Y0.2O3-s as the electrolyte and Fe-doped BaZr0.8Y0.2O3-s as the sensing electrode

A triple-conducting metal oxide, BaZr0.8-xFexY0.2O3-s (BZFY), was fabricated as a sensing electrode (SE) by doping Fe into the proton-conducting electrolyte BaZr0.8Y0.2O3-s for use in an amperometric ammonia (NH3) sensor. The effects of Fe content on the interface and electrochemical performance of the sensors were thoroughly investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal that all sensors exhibited strong interfacial bonding between the SE and electrolyte. Notably, the sensor with BaZr0.2Fe0.6Y0.2O3-s as the SE demonstrated the highest gas sensitivity and selectivity toward NH3. The Delta I value of the sensor was almost proportional to the logarithm of ammonia concentration, reaching a maximum sensitivity of 3.73 mu A/decade. This enhanced performance can be attributed to an optimal ratio of Fe3+ to Fe4+, effective modulation of oxygen vacancies, and a significant improvement in ionic conductivity. Additionally, the sensor exhibited excellent repeatability and long-term stability. Furthermore, the sensing mechanism of the sensor was elucidated.