High-performance YSZ-based mixed potential NH3 sensor has been developed and utilized with the prospect of excellent applications in in-vehicle SCR (Selective Catalytic Reduction) systems. In order to further lower the detection limit and improve the sensitivity to NH3, we prepared Ag decorated FeVO4 as sensing electrode ma terial through the NaBH4 reduction method in this work. Electrochemical methods such as cyclic voltammetry (CV), linear sweep voltammetry (LSV) and I-t curves are used to explore and compare the electrochemical catalytic activity of electrode materials. 3 mol% Ag decorated FeVO4 was considered as the best sensing electrode material because of its highest electrochemical catalytic activity and reliable stability. Also, the reaction product under the sensor’s working condition was confirmed by the online mass spectrometer. The sensor attached with 3 mol% Ag decorated FeVO4-SE could give a response of − 57 mV to 50 ppm NH3 in 3s and recover to base line in 16s, exhibiting its rapid detection ability at high temperature of 550 ◦C. Moreover, it displayed good selectivity and a low detection limit of 200 ppb. Additionally, the stability of the sensor under different oxygen concen tration and humidity was studied in detail.