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摘要
Based on the polyvalent characteristics and excellent catalytic performances of manganese and vanadium, potentiometric gas sensor using MnV2O6 sensing electrode was fabricated for NH3 detection at high temperatures. NH3 sensitivity of the sensors sintered at 700 degrees C, 750 degrees C and 800 degrees C were -52.4, -60.0 and -39.1 mV/decade respectively, and the detection limit reaches 2 ppm at 550 degrees C. 700 degrees C-sintered sensor displays the slowest response rate, and sample sintered at 800 degrees 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 NH3 below 40 ppm, sensor attached with MnV2O6 electrode has the highest responses and slowest recovery rate at operating temperature of 500 degrees C, and presents the lowest signal and fastest recovery at 600 degrees C. 550 degrees C is considered the optimal operating temperature based on high sensitivity and shortest response time. Cross sensitivity of MnV2O6 to other oxidizing/reducing gases is much lower than NH3, and it shows good anti-interference ability to oxygen/vapor content change in certain range. Polarization curve showed that the reason for high NH3 selectivity was mainly due to high electrochemical catalytic activity of MnV2O6 to NH3, and electrochemical impedance spectroscopy test proved that sensing electrode played a leading role compared with reference electrode in response process.
