A ppb-level NO2 gas sensor with ultra-high concentration shock resistance characteristics based on In2O3-In2(MoO4)3

Metal oxides are widely used because of their simple structure, low price, and excellent gas-sensitive properties. But now, the metal oxide sensor faces two challenges. One is that when the detection limit of the sensor is low, it will be affected by a high concentration of gas and fail in practical applications. Second, the metal oxide sensor is susceptible to temperature changes, resulting in inaccurate measurement results. To address the above problems, the performance of metal oxides is enhanced through doping. Indium oxide doped with various levels of indium molybdate was prepared using a two-step hydrothermal method resulting in a composite material with an n-n heterostructure. The interaction formed by the n-n heterostructure enhances the redox reaction between NO2 gas and the sensor, and the unique nano cluster structure provides more active sites for the sensor, significantly improving the gas performance of the sensor towards NO2. Sensors based on In2(MoO4)3 with a doping ratio of 4 % (the sample IM3) showed excellent gas sensitivity. The lower and upper detection limits of the sensor are 200 ppb (response is 1.46) and 150 ppm (response is 515.94), respectively. And the sensor has good resistance to ultra-high concentration (10000 ppm) nitrogen dioxide (NO2) impact. In the range of 130–170°C, the temperature has a small and linear effect on the sensor response, which is very beneficial for temperature correction of gas sensors. The sensor prepared by In2(MoO4)3 doped In2O3 composite material has a good potential for application in engineering practice.