关键词: 大气污染, 颗粒物传感器, 二氧化碳传感器, 机动车尾气排放

Abstract: Significance　With the rapid development of the national economy, the levels of industrialization and urbanization have been continuously improving, leading to a large amount of exhaust gases and pollutants being discharged into the environment and causing severe air pollution. Against the backdrop of pollution reduction and carbon emission reduction during the 14th Five-Year Plan period, the emissions of particulate matter (PM) and carbon dioxide (CO2) from heavy-duty diesel vehicles have become key mobile source emission issues. Most particulate pollution is caused by incomplete combustion, and by-products such as CO2 produced by incomplete combustion can exacerbate the urban heat island effect. Therefore, there is an urgent need to develop sensor technologies with high sensitivity and stability to accurately monitor PM and CO2 emissions from heavy-duty diesel vehicles, providing more precise emission data support for reducing pollution and carbon emission from mobile sources. Thus, the latest development progress of high-temperature in-situ PM and CO2 sensors is introduced in this paper, which is of great significance for the development of new sensors and for assisting in the monitoring and supervision of national mobile source emission in China. Progress　High temperature in-situ PM sensor is an electrostatic particle sensor with wider measurement range, higher temperature resistance peak, higher time resolution and lower measurement error. The sensor mainly includes sampling probe module and system control module. The sampling probe module is specifically composed of high-voltage electrode, protective part, metal shielding layer, concentration detection area, ceramic heater, etc. The system control module is mainly divided into micro current control module, analog-to-digital converter, controller, temperature control module, high voltage control module, communication module and data processing module. The comparison tests were carried out between the PM sensor of Zhongqiyan Automobile Inspection Center Co., Ltd. and the commercial AVL483 sensor. The experimental results show that there is a high correlation between the measured values of the two sensors. Using orthogonal distance regression algorithm, the correlation coefficient of the values of the two sensors reached 70.2% after 21 iterations. At the same time, the sensor developed by Zhongqiyan Automobile Inspection Center Co., Ltd. has more stable measurement results and more rapid dynamic response, achieving the expected sensor performance. CO2 sensor is a sensor composed of heating wire, alumina ceramic tube, NASICON solid electrolyte, sensitive electrode and reference electrode. It can reflect the concentration of CO2 in the environment by measuring the potential difference between the sensitive electrode and the reference electrode. The stability and sensitivity of CO2 sensor were improved by doping 10% Co3O4 into Na2CO3, and NASICON material was added to improve the quality of the three-phase interface and shorten the response recovery time of the sensor. The experimental team of Jilin University conducted CO2 sensor application test in China Automotive Research Center Co., Ltd. The test results show that under the relatively stable CO2 input, the test results of the in-situ CO2 gas sensor are relatively accurate, with a maximum error controlled within 6%, indicating that the sensor can realize real-time and accurate testing. Conclusions and Prospects　The high-temperature in-situ PM and CO2 sensors for vehicle exhaust introduced in this paper have made significant progress in the direction of intelligence, and their performance indicators are all higher than the international advanced level. The relative error of the electrostatic PM sensor is controlled within ±6.00%, with a concentration measurement range of 0 to 100 mg/m³, and a response time of seconds. The high-temperature NASICON solid electrolyte CO2 sensor, using Co3O4-doped Na2CO3 as the sensitive electrode material and improving the three-phase interface quality by doping NASICON material, greatly reduces the response and recovery time of the sensor, achieving a response and recovery time of seconds and a maximum error of less than 6%, which can basically meet the application requirements in the field of vehicle exhaust detection. In addition, new generation information technologies such as big data, the Internet of things and cloud computing will also play an important role in exhaust gas monitoring technology. In short, the emission monitoring technology of mobile source tail gas is developing towards high precision, low delay, and high intelligence.

Key words: air pollution, particle sensor, carbon dioxide sensor, motor vehicle exhaust emissions