Enhanced NO2 gas-sensing performance of 2D Ti3C2/TiO2 nanocomposites by in-situ formation of Schottky barrier

Abstract Two-dimensional (2D) Ti3C2 MXene, derived from the Ti3AlC2 MAX phase, is a potential candidate for gas sensing materials due to its high conductivity, but it has a shortcoming of weak sensitivity towards gases. Here, we firstly synthesized Ti3C2/TiO2 nanocomposites by in-situ growth of TiO2 on the surface of multilayer Ti3C2 MXene via a hydrothermal oxidation process, and investigated the gas-sensing performances (involving response, operation temperature and selectivity) of Ti3C2/TiO2 composites by combining experiments and first-principles calculations. The experimental results show that the hydrothermal oxidation temperature plays a key role in the morphology evolution and gas-sensing performance of Ti3C2/TiO2 composites. Compared to the pristine Ti3C2, the Ti3C2/TiO2 composites display outstanding response to NO2 gas due to the formation of a Schottky barrier at the Ti3C2/TiO2 interface, as a result of that the excellent response of ~ 1.13 to 5 ppm NO2 is achieved at room temperature. In particular, the optimal Ti3C2/TiO2 composite presents higher response value (86 times) and faster response and recovery time (2 and 3.8 times) to 100 ppm NO2 than pristine Ti3C2 at optimum temperatures, and shows good selectivity and linear response to NO2 gas. This work provides a simple process to in-situ form the Schottky barrier for improving the gas-sensing performance of pristine MXene in practical applications.