Low Operating Temperature and Highly Selective NH3 Chemiresistive Gas Sensors Based on a Novel 2D Ti3C2Tx/ZnO Composite with P-N Heterojunction

Ammonia monitoring in our daily life is significant. In this work, Ti3C2Tx/ZnO materials were prepared by hydrothermal method. The results of XRD, SEM, TEM, and XPS analyses demonstrated the successful preparation of the Ti3C2Tx/ZnO composite. Ti3C2Tx/ZnO (3:1) material exhibited the best morphology as ZnO grows evenly on it as ultrathin nanosheets. The gas sensing performance of Ti3C2Tx/ZnO, and Ti3C2Tx/ZnO (1:1, 2:1, 3:1, and 5:1) materials were studied. The Ti3C2Tx/ZnO (3:1) sensor has an excellent response to 50 ppm ammonia at a low operating temperature (-28 degrees C), and the value of response is 196%, which is the highest response in this work. Furthermore, it was found that Ti3C2Tx/ZnO (3:1) detects ammonia selectively against other volatile organic compounds at a low operating temperature (-28 degrees C). The actual lowest detection ability was measured at 1 ppm, and the corresponding response is 14%. The ultra-thin ZnO nanosheets on the Ti3C2Tx MXene and the p-n heterojunctions in Ti3C2Tx/ZnO (3:1) are designed to achieve better ammonia sensing performance. This paper provided a route to enhance the p-type characteristic of Ti3C2Tx MXene, which is meaningful to Ti3C2Tx MXene application at a low operating temperature in the future.