High-Temperature CO 2 Sensor with Second-Level Response for Diesel Engine Exhaust Gas Detection Applications

Diesel engines in the field of transportation are one of the important sources of carbon dioxide (CO2) emissions, and incomplete combustion and complex working conditions make it difficult to accurately calculate their CO2 emissions by using the intake volume. In addition, the high temperature and harsh environment of exhaust gas also put higher requirements on the response speed, stability, and high-temperature resistance of the sensor. In this study, Co3O4 was doped into the auxiliary phase Na2CO3 as a catalyst and stabilizer to improve the sensor sensitivity, and solid electrolyte NASICON was doped to improve the sensor response speed. The results show that when the doping ratio of Na2CO3 and NASICON is the same as 10 wt %, the response to CO2 of 5000 ppm can reach −67 mV, and the full-range second-level response to CO2 is realized. The detection range is up to 0–180,000 ppm, the sensitivity is −64 mV/decade, the sensor has good selectivity to CO2, the response change in the range of 20–98% RH is negligible, and the response change in 60 days is only −8.66%. This sensor had good reproducibility. In addition, the in situ on-board CO2 sensing probe and test system were developed. The sensor response was calibrated against the measurement values of standard instruments on the entire vehicle. Based on the calibration results, a regression curve was established and the vehicle was tested; the test results and the standard instrument test value deviation are basically less than 10% to verify the practicality of the component in the exhaust gas detection.