TiO2 decorated MXene nanosheets for high-performance ammonia gas sensing at room-temperature

A room-temperature sensor with superior performance to detect traces of toxic gas molecules is highly desirable. MXenes, due to their unique planar structure, higher electrical conductivity and abundant functional groups on the surface, have emerged as leading low dimensional gas sensing materials. But, the gas sensors based on Ti3C2Tx MXene possess higher detection limit and poor long-term stability, thereby limiting their applications. However, TiO2 modified Ti3C2Tx as a gas sensing platform has displayed improved ammonia sensing performance. Here, we report a facile method to prepare Ti3C2Tx/TiO2 composite via calcination of Ti3C2Tx. The experimental results indicate that the oxidation temperature plays a key role in the morphology evolution and gas-sensing performance of Ti3C2/TiO2 composites. Compared to the as obtained Ti3C2Tx, the Ti3C2Tx/TiO2 composite obtained at 200 °C displays improved response to NH3 gas due to the formation of a heterointerface between Ti3C2Tx and TiO2. Room-temperature, selective ammonia detection down to 5 ppb has been obtained. Moreover, the device displayed a stable sensing response to 10 ppb of ammonia over the RH range of 26%–90%. It also displayed higher selectivity to NH3 over other analytes including dimethyl formamide, ethanol, isopropyl alcohol, methanol, acetone, chloroform, xylene and N-methyl pyrolidone. The results suggest that by appropriate engineering of the Ti3C2Tx/TiO2 composites, ammonia sensor with improved sensing performance can be designed.