Sr1-xMxMoO4 (M= Ba, La, Sm and x=0.05) electrode materials for YSZ-based mixed-potential ammonia sensors under reducing conditionsShow affiliations

Mixed-potential gas sensors have emerged as a promising solution for real-time NH3 detection and quantification under the reducing conditions of direct ammonia-fed fuel cells (DAFCs) due to their stability in harsh thermochemical environments, simple design, and cost-effectiveness. This study evaluated the effectiveness of doping various electronegative cations (Ba-2(+), La3+, and Sm3+) at the A-site of SrMoO4 sensing electrode (SE) materials for NH3 detection under reducing conditions. The Sm3+-doped SrMoO4 SE-based sensor exhibits the highest response of -32.74 mV toward 80 ppm NH3 at 500 degrees C. The sensitivity was enhanced by 38.69% for 10 -60 ppm and 8.69% for 60 -320 ppm over undoped SrMoO4 SE. Additionally, the response and recovery times for 80 ppm NH3 were 85 s and 3.89 s faster than those of SrMoO4 SE, respectively. The response behaviors and electrochemical characteristics confirm that the sensing mechanism follows the mixed-potential model with NH3 oxidation kinetics limited by the Butler-Volmer reaction rate. Moreover, the sensor exhibited high sensitivity, selectivity, exceptional stability (<4%) toward 80 ppm NH3 (10 cycles) along with robust response under humid conditions. Thus, the proposed sensor configuration is potentially viable for real-time monitoring and quantification of ammonia in the anode compartment of DAFCs.