Response Characteristics of an Amperometric NOx-O2 Sensor at Non diffusion-Rate-Determining Conditions 2021-01-0678

Experimental results are combined with a physical understanding of an amperometric NO_x-O₂ sensor to study the effect of three main operating parameters on the sensor behavior in non diffusion-rate-determining operating conditions. The sensor response to NO_x concentration is examined over a range of sensor operating temperatures, reference cell potentials, and second sensing cell potentials. The results show that the sensor sensitivity increases gradually with the sensing cell voltage while the sensor output is almost linearly dependent on NO_x concentration for cell voltages higher than ≈ 0.25 V. The results also reveal that reducing the reference cell potential from the typical cell potential (0.42 V) reduces the sensor cross-sensitivity to O₂ particularly at high NO_x concentrations (>600 [ppm]). The results of this work provide a better understanding of the sensor behavior at different operating conditions which can be used to design new accurate sensors with different sensitivities to a variety of species in the exhaust gas. This improved understanding of the sensor has the potential to remove cross-sensitivity for emission measurements of gases containing NOx and other species in the exhaust gas such as ammonia and unburned hydrocarbons.