Resister-type sensors based on Ti3C2Tx MXene decorated In2O3 p-n heterojunction for ppb-level NO2 detection at room temperature

Real-time detection of nitrogen dioxide (NO2) gas is extremely important for the environment and human health, so the development of sensor that can detect NO2 at room temperature is high anticipation. However, there are still technical challenges to achieving excellent gas-sensitive performances with NO2 gas sensors that detect parts per billion (ppb) level at room temperature. To solve the above-mentioned problem, the In2O3/Ti3C2Tx MXene pn heterojunction gas sensors with abundant oxygen vacancies and high surface area have been synthesized by hydrothermal combined annealing. The In2O3/Ti3C2Tx-2 has high selectivity to NO2, high response (152.95) to 100 ppm NO2, low theoretical detection limit (2.87 ppb) and outstanding stability at room temperature. These excellent gas-sensitive performances can be put down to the abundant surface oxygen vacancy that provides active sites, and the p-n heterojunction that effectively regulates charge transfer behavior through conduction tunnels in the gas sensors. Furthermore, the In2O3 nanoparticles are attached between the surface and intercalation of Ti3C2Tx MXene, avoiding the oxidation of Ti3C2Tx MXene, so sensors have good stability. This work reveals the sensing mechanism of In2O3/Ti3C2Tx MXene, which provides effective guidance for the design and development of Ti3C2Tx MXene-based gas sensors.