Fabrication Of NO₂ Gas Sensor Based On Indium Oxide Nanomaterials And Research On Its Anti-humidity Performance

NO₂ is a typical atmospheric pollutant,and its efficient and rapid detection is of great importance for environmental protection.Metal oxide semiconductor gas sensors are measurement tools for the efficient detection of NO₂ gas.However,the performance of gas sensors is significantly affected by environmental humidity due to the water vapor poisoning phenomenon,which limits their wide application.Thus,it is important to develop NO₂ gas sensors with moisture resistance.Synthetic composites can modulate the interaction between the surface of the metal oxide semiconductors and water molecules,thus improving the humidity resistance of the sensors.In addition,the use of thin films to block the contact between gas-sensitive materials and water molecules is also an effective means to improve the moisture resistance of metal oxide semiconductor gas sensors.In this paper,the construction of a NO₂ gas sensor with moisture resistance and the analysis of its moisture resistance mechanism was realized by synthesizing composite materials and adding hydrophobic films,respectively,as follows:1.Graphite nanoflakes/In₂O₃ nanoflowers composite gas-sensitive materials with moisture resistance properties were synthesized by the hydrothermal method.The material exhibited excellent stability（response fluctuations within 7%）over a wide humidity range（20%-90%RH）compared to the results reported in the literature.The sensor based on the graphite nanoflakes/In₂O₃ nanoflowers composite exhibited response values up to 10 for250 ppb NO₂（80%RH）.In addition,the sensor exhibited good selectivity for NO₂,low operating temperature（75°C）,and fast response rate.The gas-sensitive mechanism analysis shows that the inherent hydrophobic nature of graphite can effectively block the interference of water molecules to In₂O₃.In addition,the surface of the hydrothermally treated graphite nanoflakes formed a large number of polar groups,which made the composite surface possess a certain water absorption function.The above reasons lead to the excellent moisture resistance of the graphite nanoflakes/In₂O₃ nanoflowers composite.2.In₂O₃ sensors with moisture resistance were constructed by adding a polytetrafluoroethylene（PTFE）hydrophobic membrane and its sensitivity performance to NO₂ gas under different ambient humidity conditions was investigated.The results showed that the gas sensor based on In₂O₃ nanoflower maintained a response value of around 180 for 1 ppm NO₂ gas at 20-90%RH due to the water vapor barrier effect of the PTFE hydrophobic membrane.Compared with the In₂O₃ sensors without the addition of the PTFE hydrophobic membrane,the introduction of the PTFE hydrophobic membrane resulted in better moisture resistance,stability,and excellent selectivity of the sensor.Due to the introduction of the PTFE membrane,the gas mass transfer rate is reduced,resulting in a longer response time for the sensor,and the response time gap decreases with increasing gas concentration.