High‐Performance Potentiometric Ammonia Sensor Based on MnCo 2 O 4 Electrodes

Ammonia, as a highly promising carbon‐free energy carrier that can potentially replace conventional natural gas and petroleum fuels in vehicular, marine, and aeronautical propulsion systems, has raised urgent requirements for high‐precision, reliable NH 3 sensing technology to eliminate potential safety risks during its large‐scale practical application, wherein the development of advanced potentiometric ammonia sensors based on functional spinel oxide materials has attracted extensive research interest. The MnCo 2 O 4 was synthesized using a hydrothermal method. The sensing electrode was prepared by sintering at temperatures ranging from 800 to 1100 °C, resulting in variable microstructures. As the sintering temperature increased, the NH 3 sensitivity of the MnCo 2 O 4 electrode initially increased and then decreased. The sensor sintered at 900 °C exhibited the highest response value of ‍−16 mV under 40 ppm NH 3 conditions, demonstrating optimal response and recovery rates and NH 3 selectivity. To further enhance the NH 3 sensitivity of MnCo 2 O 4 , the electrode was modified by 8 wt.% Pt. The modification was observed to significantly improve the electrochemical catalytic activity of the electrode, increasing the sensitivity from −13.5 to −53 mV/decade. This indicates that MnCo 2 O 4 has great potential for practical applications as a potentiometric ammonia sensor.