New Total-NOx Sensor Based on Mixed Potential for Automobiles

The new total-NOx sensors were made by laminating YSZ green sheets, on which electrodes including an NOx sensing electrode, an oxygen pump, an NOx conversion electrode, a Pt heater and a pair of thermocouples were printed and fired. The exhaust gas containing NOx(NO and NO₂), HC and CO were introduced into the cavity inside the sensor body, then HC and CO were oxidized to non-interference gases. NO was subsequently converted to NO₂ by the NOx conversion electrode at the second half cavity. Consequently, NO and NO₂ in the exhaust can be detected in total-NOx concentration as low as 10 ppm by the sensing electrode based on the mixed potential.