2D/2D {001}TiO2-/Ti3C2T composite with ultra-high sensing performance for NO2 at room temperature

The remarkable electrical conductivity, abundance of surface functional groups, and large specific surface area make 2D MXenes-based heterostructures highly promising for room temperature gas sensing applications. However, these MXenes-based heterojunctions composed of different materials may suffer from issues, such as crystal incompatibility and bandgap mismatch. Herein, the {001}TiO2-x/Ti3C2Tx composite was prepared in situ by hydrothermal process and subsequent annealing. The {001} facets of TiO2 and oxygen vacancies that provide a heightened exposure of active sites in the composite and more gas diffusion channels, as well as the formation of Schottky barriers between {001}TiO2 nanosheets and Ti3C2Tx, can synergistically enhance the gas performance. The experimental results show that the {001}TiO2-x/Ti3C2Tx composite exhibits 1.9 and 27.5 times higher than the {001}TiO2/Ti3C2Tx composite and pristine Ti3C2Tx to 10 ppm NO2 at room temperature, respectively. Moreover, the {001}TiO2-x/Ti3C2Tx composite presents the great linear response (R2 = 0.99509), selectivity, repeatability and long-term stability to NO2. Density functional theory (DFT) calculations reveal the strong interactions between the {001}TiO2-x/Ti3C2Tx and NO2, indicating excellent sensitivity and selectivity of the composite material towards NO2. This work provides an effective way to construct a series of oxygen-defective Ti3C2Tx-based composites with exposed high-energy facets for enhanced gas sensing performances.