ZnO/Ti3C2 composite with oxygen vacancies and Schottky barrier for effective detection of ppb-level NO2 at room temperature

Room-temperature detection of low concentrations of toxic and harmful gases is of great significance for the health and life of human being and contributes to long-term stability and low power consumption of gas sensors. In this work, we firstly prepared a ZnO1-x/Ti3C2 composite with rich oxygen vacancies by a hydrothermal process and subsequent annealing in hydrogen atmosphere. The experimental results reveal that the ZnO1-x/Ti3C2 composite exhibits very high responses (Delta R/Ra) of 0.03, 0.21 and 2.28 to 0.01, 1 and 10 ppm NO2 at room temperature, among which the response to 10 ppm NO2 is 2.3 and 14.2 times higher than those of ZnO/Ti3C2 composite and pristine Ti3C2, respectively. Moreover, the ZnO1-x/Ti3C2 composite presents good linear response (R2 = 0.99509), reproducibility and long-term stability to NO2. The outstanding NO2 sensing properties of ZnO1-x/Ti3C2 composite are mainly attributed to the presence of abundant oxygen vacancies and the formation of ZnO1-x/Ti3C2 Schottky barrier. Both the gas responses and calculated adsorption energies of ZnO1-x/Ti3C2 and ZnO/Ti3C2 composites to NO2, NH3, CO, HCHO and acetone demonstrate the high selectivity of the ZnO1-x/Ti3C2 composite to NO2. This work provides a new perspective on enhancing the room-temperature gas sensitivity of MOS-containing composites by constructing oxygen vacancies and heterojunction.