Ti3C2Tx@Co(OH)2/Co3O4 nanocomposites with heterojunction enhancement effect for toluene detection at room temperature

Ti3C2Tx MXene possesses excellent conductivity, tunable electronic structure, and large surface area, thereby ideal for use in gas sensors. However, Ti3C2Tx MXene is limited by low sensitivity linked to its low intrinsic activity and susceptibility to oxidation. Herein, Ti3C2Tx@Co(OH)2/Co3O4 nanocomposites were prepared by self-assembly strategy. High sensitivity to toluene at room temperature can be obtained by adjusting the input ratio of Ti3C2Tx MXene (MXCo-40). MXCo-40 obtained with 40 mg of Ti3C2Tx MXene input exhibited a remarkable response of 514 % to 100 ppm toluene, 737 times higher than Ti3C2Tx MXene, with response and recovery times of 9 s and 5 s. Ultraviolet photoelectron spectrometer, ultraviolet–visible absorbance spectroscopy, and diffuse reflection infrared fourier transform spectroscopy analyses revealed the heterojunction structure and monitored the gas-sensing reaction. The results suggested that the improved performance can be attributed to the formation of enhanced heterojunction structure, the electron-supplying ability of Co low-lying 3d orbitals, and high local charge concentration facilitating toluene polarization and bond breaking. In summary, the proposed composite structure looks promising for the preparation of Ti3C2Tx MXene-based gas sensors for enhanced gas-sensing applications.