Conductometric NO2 gas sensors achieved by design of Ti3C2Tx @ZnO heterostructures for application around 80 °C

Low-temperature, stable and highly selective behaviors are the essential indicators for evaluating gas sensors. Although ZnO has attractive stability as a sensitive material, it is still an enormous challenge to construct highly sensitive gas sensors with high selectivity at low temperatures employing ZnO. Herein, we have achieved a high-selectivity and low-temperature stable nitrogen dioxide (NO2) gas sensor by composite of Ti3C2Tx flakes with ZnO nanorods by facile hydrothermal process. As a results, Ti3C2Tx doped with 3 mmol ZnO exhibits the highest sensitivity (190%, 50 ppm), outstanding selectivity and stability for NO2 gas, due to the presence of multiple Schottky barriers (SB), which are originated from the heterostructure of Ti3C2Tx and ZnO. The metal-like properties of Ti3C2Tx can provide multiple electron transfer channels and accelerate the electron transfer rate. Moreover, the adsorption of more NO2 molecules can also enhance the sensitivity of sensitive material as ZnO, which is rich in adsorption sites, can form interactions with NO2. The first-principles calculation supported a preferential adsorption of NO2 on ZnO nanorods. Our investigation facilitates the appropriate design of high-performance gas sensors at lower operating temperature.