Humidity-Independent, Highly Sensitive and Selective NO2 Sensor Based on In2O3 Nanoflowers Decorated With Graphite Nanoflakes

Metal oxide semiconductor (MOS) gas sensor is an effective tool for NO ₂ detection. However, their performance is seriously influenced by humidity due to water vapor poisoning, and it remains a challenge to develop an anti-humidity NO ₂ MOS sensor. In this work, a humidity-independent, highly sensitive and selective NO ₂ sensor based on In ₂ O ₃ nanoflowers decorated with graphite nanoflakes was fabricated, which exhibited excellent anti-humidity and stability (response fluctuation within 7%) in a wide relative humidity (RH) range of 20% - 90%. The fabricated sensor had a high response of 10 to ppb level NO ₂ (RH 80%). Besides, the sensor exhibited good selectivity, low operating temperature (75 °C) and rapid response speed (50 s to 5 ppm NO ₂ ). The reason for the excellent anti-humidity function was investigated. Large amounts of polar groups were formed on the graphite nanoflakes after hydrothermal treatment, which enhanced the interaction between the graphite and In ₂ O ₃ and made the surface of the composites have a strong water absorption function. Moreover, the intrinsic hydrophobic property of the graphite can effectively block the interference of water vapor to the moisture-sensitive In ₂ O ₃ . Our work provides a new idea for enhancing the anti-humidity performance of the MOS sensors and can broaden their applications in a variety of complex environments.