Design And Research Of Gas Sensors For Vehicle Exhaust Detection

With the progress of technology and human development,motor vehicles have become one of the main means of transportation for human travel,and the consequent exhaust emissions from motor vehicles have caused pollution to the atmosphere.In addition,with the increase in the popularity of ethanol gasoline,the number of motor vehicles using ethanol gasoline is also increasing year by year,in which nitrogen dioxide and acetone are the main emissions of ethanol gasoline combustion,and excessive nitrogen dioxide and acetone have a significant risk to the atmosphere and human health.Therefore,it is important to develop gas sensors for the detection of nitrogen dioxide and acetone.Metal oxide semiconductor gas sensors with high sensitivity,low lower detection limit and fast response have become an important research direction for gas sensors.In this paper,tin oxide and indium oxide metal semiconductor materials are used as substrates and modified by doping with rare earth and precious metal elements to investigate the changes of their gas-sensitive properties.And the prototype devices of the sensors were prepared and the gas-sensitive performance tests were carried out as follows:（1）SnO₂ and Ce/SnO₂ nanomaterials were prepared by a one-step hydrothermal method for the detection of NO₂ gas.The experimental results show that the SnO₂material achieves the best response to NO₂ gas at 80°C,with a sensitivity of 86.3 for50 ppb NO₂.In particular,the 1%Ce/SnO₂ material exhibits good resistance to moisture,with the response remaining essentially constant over the humidity range of 30%-50%.The mechanism of moisture resistance is explained in detail in the paper using the rapid regenerative oxidation/reduction reactions of Ce⁴⁺and Ce³⁺.（2）For acetone gas,In₂O₃ nanoparticle samples were synthesized by hydrothermal method to design and develop gas sensors.The experimental results show that the In₂O₃material exhibits good gas-sensitive performance for acetone detection.the optimum operating temperature of the In₂O₃ material is 280°C,and the response to 100 ppm acetone reaches 41.8.and has good response recovery characteristics,with response time and recovery time around 10 s.In order to reduce the device power consumption,the In₂O₃ material was modified with noble metal Pt and doped with rare-earth elements Ce,respectively.The results show that Pt and Ce doped In₂O₃ samples reduce the optimum operating temperature of pure In₂O₃ samples,which is 220℃,by 60℃.The mechanism of the temperature reduction is mainly due to the spillover effect of the metal and the catalytic property of Ce elements that increase the surface activity of the material,resulting in the reduction of the optimal operating temperature of the device.