Ammonia Sensing Performance of Manganese Vanadate at High Temperature

Based on the polyvalent characteristics and excellent catalytic performances of manganese and vanadium, potentiometric gas sensor using MnV
₂
O
₆
sensing electrode was fabricated for NH
₃
detection at high temperatures. NH
₃
sensitivity of the sensors sintered at 700 °C, 750 °C and 800 °C were −52.4, −60.0 and −39.1 mV/decade respectively, and the detection limit reaches 2 ppm at 550 °C. 700 °C-sintered sensor displays the slowest response rate, and sample sintered at 800 °C shows the lowest and unstable responses. Excessive temperature promotes the destruction of electrode microstructure, thus leads to the deterioration of sensor’s sensitivity. For NH
₃
below 40 ppm, sensor attached with MnV
₂
O
₆
electrode has the highest responses and slowest recovery rate at operating temperature of 500 °C, and presents the lowest signal and fastest recovery at 600 °C. 550 °C is considered the optimal operating temperature based on high sensitivity and shortest response time. Cross sensitivity of MnV
₂
O
₆
to other oxidizing/reducing gases is much lower than NH
₃
, and it shows good anti-interference ability to oxygen/vapor content change in certain range. Polarization curve showed that the reason for high NH
₃
selectivity was mainly due to high electrochemical catalytic activity of MnV
₂
O
₆
to NH
₃
, and electrochemical impedance spectroscopy test proved that sensing electrode played a leading role compared with reference electrode in response process.