The Research Of The Mixed-potential-type Zirconia-based Nox Ssnsor Using For The Controlling Of Automobile Exhaust

This paper focuses on the gas sensing properties of the mixed-potential-typeNO₂sensor based on yttria stabilized zirconia （YSZ） and NiO electrode. The sensingperformance of the sensor was improved by modifying the three-phase boundary（TPB） and controlling the microstructure of NiO sensing electrode synthesized withthe microwave.Firstly, hydrofluoric acid with different concentrations （10%,20%and40%）was used to corrode YSZ substrate to obtain large superficial area of TPB. Thescanning electron microscope and atomic force microscopic images showed that the40%HF could form the largest superficial area at the same corroding time （3h）. Thesensitivity of the sensor using the YSZ plate corroded with40%hydrofluoric acid to20-500ppm NO₂was76mV/decade at850°C, which was the largest among theexamined HF concentrations. It was also seen that the sensor showed a goodselectivity and speedy response kinetics to NO₂.Secondly, the sensing characteristics of the sensors have been improved bycontrolling the microstructure of NiO sensing electrode synthesized with themicrowave. The microstructure of NiO strongly depended on the microwavetreatment temperature and the sintering temperature. The largest sensitivity of thesensor was obtained by using the NiO synthesized at60℃and sintered at1200℃, theslope of the dependence of EMF on the NO₂concentration in the range of20-500ppm was54mV/decade at850°C. It was also seen that the sensor showed a fastresponse and recovery kinetics to NO₂.At last, on the basis of the measurements of anodic and cathodic polarizationcurves, as well as the complex impedance of the device, the sensing mechanism wasconfirmed to involve a mixed potential at the oxide sensing electrode. In conclusion, the mixed-potential-type zirconia-based NOx sensor in this paperhas simple structure, high sensitivity, good selectivity, fast response and recoveryspeed, chemical and thermal stability. It has potential important application in carexhaust monitoring area, and very important significance and prospect.