Abstract
Planar potentiometric NO2 sensors based on 8YSZ (8 mol% Y2O3-doped ZrO2) were prepared with WO3 sensing electrode material. The various electrode microstructures prepared by different sintering temperatures were characterized by field emission scanning electron microscopy (SEM), and the microstructure influences on the sensors' performances were investigated. The sensor sintered at 800°C, with the most reaction sites, moderate adsorption sites and appropriate electrode thickness, exhibits the highest NO2 voltage response. While the sensor sintered at 750°C exhibits the lowest NO2 sensitivity because of the strongest gas-phase catalytic consumption in the WO3 sensing electrode. Based on the results of SEM characterization and electrochemical impedance spectroscopy tests, the difference in NO2-sensing performance was attributed to different amounts of electrochemical reaction sites at three-phase boundary, adsorption sites and different degrees of gas-phase catalysis.
Highlights
The air is continuously polluted by chemical, automobile and petrochemical industries due to rapid industrialization
scanning electron microscopy (SEM) micrographs of the cross sections of WO3 sensing electrode (WO3-SE) are shown in figure 2
It is seen that WO3-SEs sintered at various temperatures have different thicknesses and there is some variability in the thickness throughout the same electrode
Summary
The air is continuously polluted by chemical, automobile and petrochemical industries due to rapid industrialization. As one of the most important parameters, electrode sintering temperature could affect the microstructure as well as the sensing electrode/YSZ interface. Based on plenty of earlier publications regarding WO3-SE potentiometric sensors, it could be found that the difference between their sintering procedures is obvious, and they were 7008C for 3 h [2], 7508C for 3 h [3], 8008C for 2 h [7] and 8008C for 10 h [11] Such big differences suggest that in order to obtain excellent gas-sensing performance, the selection of the sintering procedure for the sensing electrode preparation is very important. After sintering processes at various temperatures, sensing electrode microstructures and NO2-sensing characteristics of different sensors were tested. The influences of the sintering temperature on the electrode microstructures as well as the sensing properties of NO2 sensors were examined and analysed
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