氧气对NO_x传感器气敏特性的影响

Affection of O_2 to the Sensing Behavior of NO_x Sensor

实验采用丝网印刷技术制作了以钇稳定氧化锆固体电解质(YSZ)为固体电解质、NiO为敏感电极和Pt为参考电极的混合电位型NOx传感器,并在高温(450～750℃)含NO和O2气氛中测试其气敏性能。测试结果显示该传感器在450～500℃和550～750℃时分别表现为电势幅值随温度升高而减小的正电势和负电势;同一NO浓度下,电势和半圆弧型阻抗谱只是随着O2含量在一定范围内的增大而分别增大和缩小。考虑到O2会把NO氧化成NO2,同时结合对传感器的理化性能、响应电势和阻抗谱及工作机理的的分析,研究了O2对NOx传感器气敏性能的影响。

The mixed potential type NOx sensor using yttria stabilized zirconia（YSZ） electrolyte with a NiO sensing electrode and a Pt counter electrode was prepared by means of screen-printing technique and used to detecte for NOx at 450~750 ℃. Its microstructure was characterized by X-ray diffraction（XRD） and scanning electron microscope（SEM）. At a fixed temperature, the electromotive force（ΔEMF） values were almost linear to the logarithm of NO concentration but positive and negative at lower and higher temperature respectively. Furthermore, the ΔEMF values increased and the semicircular arcs observed in complex impedance spectra（Nyquist plots） in the frequency range of 0.01 Hz to 100 kHz shrinked with the O2 concentration increasing within a certain range. In view of NO could be oxidized into NO2 in O2 containing atmosphere, the sensing characteristic of sensor varied with the concentration of O2 in the sample gas was studied and discussed in combination with the microstructure of electrode as well as the complex impedance spectra and the related sensing principle.